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Funding Information: This work has been carried out within the framework of the EUROfusion Consortium, partially funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200—EUROfusion). The Swiss contribution to this work has been funded by the Swiss State Secretariat for Education, Research and Innovation (SERI). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union, the European Commission or SERI. Neither the European Union nor the European Commission nor SERI can be held responsible for them. Further, the assistance provided by Friedemann Herold was greatly appreciated. Publisher Copyright: © 2023 The Author(s). Published on behalf of IAEA by IOP Publishing Ltd. We compute reconstructions of 4D and 5D fast-ion phase-space distribution functions in fusion plasmas from synthetic projections of these functions. The fast-ion phase-space distribution functions originating from neutral beam injection (NBI) at TCV and Wendelstein 7-X (W7-X) at full, half, and one-third injection energies can be distinguished and particle densities of each component inferred based on 20 synthetic spectra of projected velocities at TCV and 680 at W7-X. Further, we demonstrate that an expansion into a basis of slowing-down distribution functions is equivalent to regularization using slowing-down physics as prior information. Using this technique in a Tikhonov formulation, we infer the particle density fractions for each NBI energy for each NBI beam from synthetic measurements, resulting in six unknowns at TCV and 24 unknowns at W7-X. Additionally, we show that installing 40 LOS in each of 17 ports at W7-X, providing full beam coverage and almost full angle coverage, produces the highest quality reconstructions.

Nuclear weapons are an ever-present danger which threatens our very existence, which is whymany call for total nuclear disarmament. To do this, we need to know how many nuclear bombsthere are in the world. However, to be sure that the true number is given, we must useapproximations and simulations to determine the nuclear capacity of a given country.Additionally, to know that these numbers are accurate, sensitivity studies are carried out.In this case, such a study was executed to measure the sensitivity of design and operationalparameters of three reactors: Ågesta, NRX, and CANDU, with respect to their plutoniumproduction and quality. The parameters of interest are power density, fuel temperature, fueldensity, fuel rod thickness, moderator temperature, moderator density, coolant temperature,coolant density, pitch, initial enrichment, and cycle length.The study relied on the simulation tool Serpent, which is a Monte-Carlo code for nuclearreactions. The parameters of interest were altered one at a time, usually by ±10% of theirnominal value, to see how the amount of plutonium changes, as well as its quality.The result showed that the power density and initial enrichment had the greatest impact onplutonium production, however, the biggest factor in terms of plutonium grade was the cyclelength. After just 30 days, the plutonium will decrease from weapon’s grade to reactor gradequality, which marks the clearest difference between how a reactor would be run for civilian orweapon purposes. Other parameters like fuel temperature and coolant temperature and densitydid not affect the plutonium in any significant fashion.

Lighting comprises a large part of the global electricity consumption as of today, and the use of lighting in illumination and displays is only projected to grow. It is therefore imperative to meet this energy demand, not only by means of greener energy production, but also with materials that are both more efficient to fabricate as well as to use. Low cost and energy efficient light sources therefore play an important role in minimizing further greenhouse emissions from the way we choose to live. Metal halide perovskites are a group of semiconductors that have received a great amount of attention during the past years due to impressive - and continuously increasing - performance as active materials implemented in solar cells and light emitting diodes. This is due to highly desirable optoelectronic properties combined with low-cost, solution-processable fabrication methods. Simple bandgap-tunability is easily achieved by compositional and dimensional engineering, allowing perovskite emission to span a broad wavelength region from ultraviolet to near infrared. As with previous technologies, attaining stable, bright, and pure blue light has proven difficult also in metal halide perovskites. This thesis investigates some of the challenges in achieving blue emission in mixed-halide and mixed-dimensional perovskites for light-emitting-diode applications. Mixed-halide alloying provides the most straightforward way of tuning the bandgap of perovskites. Unfortunately, mixed bromide/chloride-perovskites (used to achieve blue light) suffer from both spectral and temporal instabilities, as well as severe luminescence quenching at the large chloride contents necessary for blue emission. The spectral instability arises from a segregation of halides into regions of differing halide content, and hence different bandgap, resulting in a shift in emission color during operation. Although the origins of the poor temporal stability of perovskite light emitting diodes are manifold, one of the main problems are the low barriers for halide migration under the applied electric field during operation, rapidly degrading the device properties. We first find that compositional heterogeneities, stemming from rapid uncontrolled film growth, both lowers the threshold for further halide segregation as well as serves as centers for non-radiative recombination, resulting in reduced luminescence yield. We show that by carefully moderating the crystallization dynamics it is possible to achieve films with a homogeneous composition, thereby mitigating the negative effects arising from material inhomogeneities. We identify means of how growth environment, stoichiometric tuning and chelating additives can be used to favorably control film formation and provide guidelines that can be more widely applied in the fabrication of perovskite films and devices. We continue by investigating the role of Br/Cl-alloying on device efficiency and stability in green to blue emitting perovskite LEDs. We find that chloride incorporation, while having only a minor impact on efficiency at moderate levels, detrimentally affects device stability even in small amounts. We ascribe this phenomenon to an increased mobility of halogen ions in the mixed-halide lattice resulting from an increased chemically and structurally disordered landscape with reduced migration barriers. We assign this as the major obstacle towards stable blue-emitting mixed-halide perovskite light emitting diodes. In the last work we investigate blue emitting mixed-dimensional Ruddlesden-Popper perovskites (RPPs) comprising of multiple-quantum-well-structures of varying bandgap. Successful implementation in LEDs has been attributed to efficient carrier funneling from large bandgap (donor) regions to low bandgap regions (acceptors) resulting in improved luminescence yields due to trap state filling from the locally increased carrier density. However, due to the enhanced carrier concentrations in acceptor domains, Auger recombination quickly outcompetes radiative recombination mechanisms already at moderate pump fluences or carrier injection densities in RPPs. We show that by moderating the inter-well carrier transfer, while at the same time providing adequate defect passivation, high quantum yields can be maintained even at large carrier densities. We thereby show that RPPs can support a large density of carriers without compromising luminescence efficiency, paving the way for their use in high brightness applications by engineering the funneling and recombination processes in these materials. The work in this thesis provides new insights on various dynamical processes in metal halide perovskites aimed at light emitting applications. The hope is that it will contribute toward the understanding of these systems and help in bringing these materials closer to practical use. Att på olika sätt att lysa upp världen omkring oss har alltid varit oumbärligt för oss människor, inte minst i mörka Sverige, och i vårt moderna samhälle har ljuskällor tagit en mer essentiell plats än någonsin tidigare. Numera använder vi dem inte bara till att lysa upp vår omvärld, utan också för att tillhandahålla information var vi än befinner oss. Denna användning är något som bara spås öka med tiden. Trots att artificiell belysning har utvecklats och blivit allt mer effektiv står den för en betydande del av världens energikonsumtion. Det är därför av stor vikt att hitta nya lösningar som är både mer energieffektiva att tillverka samt att använda. Metall-halid-perovskiter är en grupp material som rönt stora framgångar som solcellsmaterial, där de efter endast lite mer än ett decenium av forskning är uppe och tävlar med väletablerade material med avseende på effektivitet. Deras stora charm ligger i en kombination av billiga beståndsdelar, simpel tillverkning och utmärkta egenskaper, och har träffande hänvisats till som den fattiges högeffektiva halvledare. Som lysdiodmaterial har de dessutom visat sig vara lovande kandidater till att komplettera eller ersätta mycket av dagens teknologi genom uppvisad god effektivitet, hög färgrenhet och möjlighet att kontrollera deras färg på till synes okomplicerade sätt. Genom att reglera förhållandet mellan de ingående beståndsdelarna som utgör perovskiten kan man ändra ljuset de avger från nära-infrarött till ultraviolett kontinuerligt, vilket inkluderar alla färger vi kan uppfatta med våra ögon och lite därtill. Detta görs lättast genom att styra halten mellan jod, brom och klor i materialen, men färgen går också att ändra genom att krympa materialen till väldigt små dimesnioner. Detta ger en många möjligheter att designa perovskitmaterial för en mängd olika ljustillämpningar. Denna avhandling rör perovskiter för blått ljus, vilket är essentiellt både för färgskärmar, där blått ljus alltid är en av tre ingående primärfärger, och för belysning där blått ljus görs till vitt i en nedkonverteringsprocess. Att tillverka perovskiter som avger blått ljus har dock visat sig vara lättare sagt än gjort. Ett problem som gäckat fältet är att blå perovskitlysdioder blir gröna när man använder dem. Detta har sin grund i att brom och klor, som används i kombination för att få blått ljus, separerar under användning och bildar bromoch klorrika områden, vilka har annan färg än blandningar utav dem. I den första studien visar vi att det redan under tillverkningen kan bildas små sådana områden, vilka sen är drivande i färgskiftningen under anvädning. Genom att modifiera tillverkningen och sakta ned perovskittillväxten visar vi att dessa områden kan minimeras, vilket har till följd att blå lysdioder håller sig blå. I en lysdiod vill man att all elektrisk ström som skickas in omvandlas till ljus. De elektroner som utgör strömmen kan dock fastna i imperfektioner, så kallde defekter, i materialet. När de fastnar så kan de ej längre bidra till att producera ljus. I en uppföljningsstudie visar vi att dessa brom- och klorrika områden inte bara gör perovskiten färginstabil, de drar också ned effektiviteten genom att introducera en mängd defekter. Genom att homogenisera materialet kan också mängden av dessa defekter minimeras, och lysdioderna göras mer effektiva. Ett av de största problemen för perovskitlysdioder i allmänhet, och blå perovskitlysdioder i synnerhet, är dess dåliga driftstabilitet. Till skillnad från kommersiella lysdioder, som kan hålla i decennier, så har blå perovskitdioders livslängd istället länge mätts i minuter, eller i bästa fall nu i timmar. Det är vedertaget att en stor del i detta kommer av att joner, elektriskt laddade atomer och molekyler, i dessa material rör på sig när man lägger på en spänning för att driva lysdioden. När dessa vandrar genom materialet påverkas lysdiodens elektriska egenskaper negativt. I den tredje studien visar vi att detta förvärras i brom- och klorbladningar, där ju mer klor vi adderar, desto sämre blir driftstabiliteten. I ett perfekt material sitter atomerna prydligt ordnade i förhållande till varandra, och det är med viss svårighet en jon rör sig genom materialet. När klor tillsätts så skapas oordning, och nya lättare vägar för joner att röra sig genom materialet introduceras vilket leder till än sämre stabilitet. Vi visar därmed vikten av att ”låsa” fast de rörliga jonerna genom att skapa välstrukturerade material för att kunna realisera stabila blå perovskitlysdioder. I den sista studien undviker vi de svårigheter som kommer med att blanda brom och klor. Istället använder vi klorfria perovskiter och justerar ljuset genom att tillverka perovskiter bestående av tunna (några atomer tjocka) lager, vilka lyser blått. Under tillverkning så bildas oftast en blanding utav lager av olika tjocklek samtidigt i dessa material. När fria laddningar introduceras, till exempel då man skickar in en ström som i en lysdiod, så kanaliseras de och ansamlas mycket effektivt i de delar av materialet som består av tjockast perovskiter. Detta har positiva effekter såsom att tidigare nämna defekter snabbt fylls och oskadligörs, vilket gör dessa perovskiter ljuseffektiva. Denna effektiva kanalisering är något som tidigare eftersträvats starkt och många metoder för att förbättra kanaliseringen har undersökts. Vid höga strömmar så leder denna ansamling av laddningar dock till skadliga processer där laddningarna istället för att avge ljus omvandlar energin till värme. Detta gör lysdioderna mindre ljusstarka och försämrar hållbarheten. Vi visar att genom att gå emot tidigare principer om att maximera nämnda kanalisering, och istället försämra den, kan de negativa effekterna minimeras och ljusstarka perovskiter kan realiseras även vid höga strömmar. Sammanfattningsvis så leder arbetet i denna avhandling till nya insikter om dynamiska processer hos metall-halid-perovskiter, både under tillverkning och användning. Förhoppningen är att det ska bidra till förståelsen av dessa system och hjälpa till att föra dessa material närmare praktisk användning.

Spore-forming pathogenic bacteria are adapted for adhering to surfaces, and their endospores can tolerate strong chemicals making decontamination difficult. Understanding the physico-chemical properties of bacteria and spores is therefore essential in developing antiadhesive surfaces and disinfection techniques. However, measuring physico-chemical properties in bulk does not show the heterogeneity between cells. Characterizing bacteria on a single-cell level can provide mechanistic clues usually hidden in bulk measurements. This paper shows how optical tweezers can be applied to characterize single bacteria and spores, and how physico-chemical properties related to adhesion, fluid dynamics, biochemistry, and metabolic activity can be assessed.

Wavepacket is a program to simulate the dynamics of a wave packet interacting with a time-dependent potential, with the time-dependent Schrödinger equation being solved on a one-, two-, or three-dimensional spatial grid using the split operator method. This new version fixes bugs present in the original program. This research was conducted using the resources of High Performance Computing Center North (HPC2N).

Thermochemical energy conversion processes, such as combustion and gasification, are applied worldwide for generation of electricity, heat and synthesis of chemicals. Today, these processes are mostly run on non-renewable, fossil fuels and constitute a major source of carbon dioxide emissions. A promising renewable energy source with low net carbon dioxide emissions is biomass, in particular rest products from agriculture and forestry. However, biomass usually contains high amounts of volatile inorganic compounds, such as chlorine, potassium (K) and phosphorus (P), which lead to ash-related operational issues, including deposit build-up, slagging and corrosion. Therefore, efficient utilization of biomass requires knowledge of the chemistry and fate of the inorganic compounds during thermochemical conversion. Due to the reactive, high-temperature environments in those processes, gaseous compounds are preferably measured in situ using optical techniques. This thesis mainly deals with the development of a laser-based technique for simultaneous in situ detection and quantification of the main gaseous K species in biomass combustion and gasification: atomic K, potassium hydroxide (KOH) and potassium chloride (KCl). The novel method combines photofragmentation (PF) with tunable diode laser absorption spectroscopy (TDLAS) and achieves sub-ppm detection limits for all three K species for a path length of 2 cm and a time resolution of 20 ms. Recording the ns-µs PF signal decay due to fragment recombination allows probing the K reaction kinetics. Together with TDLAS sensors for water, methane and gas temperature, the PF-TDLAS system was employed to characterize biomass reactors from laboratory- to pilot-scale. The results were compared to predictions by numerical models. In addition, PF-TDLAS was employed for quantitative wide-field imaging of K species in a laboratory flame during KCl salt and biomass conversion. Finally, in situ detection of phosphorus pentoxide (P4O10) with a time resolution of 140 ms was demonstrated using broadband infrared absorption spectroscopy. Absorption line strengths of P4O10 at temperatures relevant for combustion were determined for the first time. The techniques presented in this thesis can provide unique experimental data for validation and further development of numerical models and advance the understanding of K species chemistry during solid fuel conversion, which is needed to facilitate the utilization of biomass in the energy system.

A novel piezo-activated luminescent material with wide range modulation of the luminescence wavelength and a giant intensity enhancement upon compression was prepared using a strategy of molecular doping. The doping of THT molecules into TCNB-perylene cocrystals results in the formation of a weak but pressure-enhanced emission center in the material at ambient pressure. Upon compression, the emissive band from the undoped component TCNB-perylene undergoes a normal red shift and emission quenching, while the weak emission center shows an anomalous blue shift from 615 nm to 574 nm and a giant luminescence enhancement up to 16 GPa. Further theoretical calculations show that doping by THT could modify intermolecular interactions, promote molecular deformation, and importantly, inject electrons into the host TCNB-perylene upon compression, which contributes to the novel piezochromic luminescence behavior. Based on this finding, we further propose a universal approach to design and regulate the piezo-activated luminescence of materials by using other similar dopants.

In this compilation thesis, three different quantum mechanical systems are presented. All three have in common that they are one-dimensional quantum systems which, each in their own way, can be seen as analogous to other quantum systems. Chapter 2 is an introduction which takes on the ambitious task to guide the reader from standard quantum mechanical theory to the theory of condensed matter physics. In chapter 3 I present a theory for creating co- herent oscillations in the adiabatic eigenstates of time-periodic quantum systems. These are directly analogous to so-called Bloch oscillations which appear for electrons in periodical potentials which are subjected to a constant force. Chapter 4 concerns how phonon physics, in particular the Peierls instability, can be mimicked in systems of interacting ultacold quantum mechanical gases. In chapter 5, I present quantum mechanical circuits (circuit QED). We propose a circuit where the low-energy physics is analogous to a strongly interacting generalized spin chain, where the so-called superradiance directly correspond to a polarized Ising phase.

QC 2023-06-08

A new series of five highly emissive binuclear heteroleptic pyridyltriazole-Cu(i)-phosphine complexes 1-5 was synthesized and examined by different experimental (IR, elemental and thermogravimetric analysis, single crystal X-ray diffraction technique, UV-vis and fluorescence spectroscopy) and quantum chemical aproaches. Complexes 1-5 exhibited excellent stimuli-responsive photoluminescent performance in the solid state at room temperature (quantum yield (QY) = 27.5-52.0%; lifetime (tau) = 8.3-10.7 mu s) and when the temperature was lowered to 77 K (QY = 38.3-88.2; tau = 17.8-134.7 mu s). The highest QY was examined for complex 3 (52%) that can be explained by the small structural changes between the ground S-0 and exited S-1 and T-1 states leading to the small S-1-T-1 triplet gap and efficient thermally-activated delayed fluorescence. Moreover, complex 4 demonstrates reversible mechanochromic and excitation dependent luminescence. Funding Agencies|Russian Science Foundation [22-73-00043]; Ministry of Education and Science of Ukraine [0121U107533, 0122U000760]; Swedish Research Council [2020-04600]

As the most abundant element in the universe after hydrogen and helium, oxygen plays a key role in planetary, stellar, and galactic astrophysics. Its abundance is especially influential on stellar structure and evolution, and as the dominant opacity contributor at the base of the Sun's convection zone it is central to the discussion around the solar modelling problem. However, abundance analyses require complete and reliable sets of atomic data. We present extensive atomic data for O I, by using the multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods. Lifetimes and transition probabilities for radiative electric dipole transitions are given and compared with results from previous calculations and available measurements. The accuracy of the computed transition rates is evaluated by the differences between the transition rates in Babushkin and Coulomb gauges, as well as by a cancellation factor analysis. Out of the 989 computed transitions in this work, 205 are assigned to the accuracy classes AA-B, that is, with uncertainties less than 10%, following the criteria defined by the National Institute of Standards and Technology Atomic Spectra Database. We discuss the influence of the new log(gf) values on the solar oxygen abundance and ultimately advocate $\log\epsilon_{\mathrm{O}}=8.70\pm0.04$., Comment: 13 pages, 5 figures; Accepted for publication in Astronomy & Astrophysics

grasp is a software package in Fortran 95, adapted to run in parallel under MPI, for research in atomic physics. The basic premise is that, given a wave function, any observed atomic property can be computed. Thus, the first step is always to determine a wave function. Different properties challenge the accuracy of the wave function in different ways. This software is distributed under the MIT Licence.

With the growing need for secure and high-capacity communications, innovative solutions are needed to meet the demands of tomorrow. One such innovation is to make use of the still unutilized spatial dimension of light in communications, which has promising applications in both enabling higher data traffic as well as the security protocols of the future in quantum communications. The perhaps most promising way of realizing this technology is through spatial division multiplexing (SDM) in optical fibers. There are many challenges and open questions in implementing this, such as how perturbations to the signal should be kept under control and which type of optical fiber to use. Consequently, this thesis focuses on the implementation of SDM in few-mode fibers where the perturbation effects on the spatial distribution have been investigated. Following this investigation, an implementation of adaptive spatial mode control using a motorized polarization controller has been implemented. The mode control has been done with the focus on having relevance for quantum technology applications such as Quantum Key Distribution (QKD) and quantum random number generation (QRNG) but also for spatial division multiplexing (SDM) for general communications. For this reason, two evaluation metrics have been optimized for: extinction ratio and equal amplitude. The control algorithm used is an adaptation of the optimization algorithm Stochastic Parallel Gradient Descent (SPGD). Control has been achieved in stabilizing the extinction ratio of LP11a and LP11b over 12 hours with an average extinction ratio of 98 %. Additionally, equal amplitude between LP11a and LP11b has been achieved over 1 hour with an average relative difference of 0.42 % and 0.45 %. Out of the perturbation effects investigated; temperature caused large disturbances to the signal which later is corrected for with the implemented algorithm.

We present the first experimental application of coherent Raman spectroscopy (CRS) on the ro-vibrational ν2 mode spectrum of methane (CH4). Ultrabroadband femtosecond/picosecond (fs/ps) CRS is performed in the molecular fingerprint region from 1100 to 2000 cm−1, employing fs laser-induced filamentation as the supercontinuum generation mechanism to provide the ultrabroadband excitation pulses. We introduce a time-domain model of the CH4 ν2 CRS spectrum, including all five ro-vibrational branches allowed by the selection rules Δv = 1, Δ J = 0, ±1, ±2; the model includes collisional linewidths, computed according to a modified exponential gap scaling law and validated experimentally. The use of ultrabroadband CRS for in situ monitoring of the CH4 chemistry is demonstrated in a laboratory CH4/air diffusion flame: CRS measurements in the fingerprint region, performed across the laminar flame front, allow the simultaneous detection of molecular oxygen (O2), carbon dioxide (CO2), and molecular hydrogen (H2), along with CH4. Fundamental physicochemical processes, such as H2 production via CH4 pyrolysis, are observed through the Raman spectra of these chemical species. In addition, we demonstrate ro-vibrational CH4 v2 CRS thermometry, and we validate it against CO2 CRS measurements. The present technique offers an interesting diagnostics approach to in situ measurement of CH4-rich environments, e.g., in plasma reactors for CH4 pyrolysis and H2 production.

Anti-perovskites A3SnO (A = Ca, Sr, and Ba) are an important class of materials due to the emergence of Dirac cones and tiny mass gaps in their band structures originating from an intricate interplay of crystal symmetry, spin-orbit coupling, and band overlap. This provides an exciting playground for modulating their electronic properties in the two-dimensional (2D) limit. Herein, we employ first-principles density functional theory (DFT) calculations by combining dispersion-corrected SCAN + rVV10 and mBJ functionals for a comprehensive side-by-side comparison of the structural, thermodynamic, dynamical, mechanical, electronic, and thermoelectric properties of bulk and monolayer (one unit cell thick) A3SnO anti-perovskites. Our results show that 2D monolayers derived from bulk A3SnO anti-perovskites are structurally and energetically stable. Moreover, Rashba-type splitting in the electronic structure of Ca3SnO and Sr3SnO monolayers is observed owing to strong spin-orbit coupling and inversion asymmetry. On the other hand, monolayer Ba3SnO exhibits Dirac cone at the high-symmetry Γ point due to the domination of band overlap. Based on the predicted electronic transport properties, it is shown that inversion asymmetry plays an essential character such that the monolayers Ca3SnO and Sr3SnO outperform thermoelectric performance of their bulk counterparts.

The emission efficiency of organic semiconductors (OSCs) often suffers from aggregation caused quenching (ACQ). An elegant solution is aggregation-induced emission (AIE), which constitutes the design of the OSC so that its morphology inhibits quenching π–π interactions and non-radiative motional deactivation. The light-emitting electrochemical cell (LEC) can be sustainably fabricated, but its function depends on motion of bulky ions in proximity of the OSC. It is therefore questionable whether the AIE morphology can be retained during LEC operation. Here, we synthesize two structurally similar OSCs, which are distinguished by that 1 features ACQ while 2 delivers AIE. Interestingly, we find that the AIE-LEC significantly outperforms the ACQ-LEC. We rationalize our finding by showing that the AIE morphology remains intact during LEC operation, and that it can feature appropriately sized free-volume voids for facile ion transport and suppressed non-radiative excitonic deactivation.

Single crystals of CaF2, cleaved along the (1 1 1) plane, were irradiated by 35Cl, 39K, 52Cr, 58Ni, 79Br and 197Au ions with energies from 2 to 48 MeV, charge states from 1+ to 11+ and ion fluences from 2e10 to 1e13 ions/cm2. The surface properties of the irradiated samples were studied using Atomic Force Microscopy in contact mode. Nanoscale surface structures were observed for some surfaces irradiated by Cl, K, Cr, Ni, Br and Au ions. Thresholds for nanostructure formation were found in terms of projectile ion velocity and electronic stopping power (Se). Clear surface modification was observed for projectiles with specific energies above approximately 0.04 MeV/u. The threshold in Se for the generation of distinct triangular structures was observed to be velocity-dependent. The average formation efficiency, referring to the ratio of the number of distinct nanostructures observed on the surface to the number of incident ions, as well as the average height of nanostructures increases with Se.

In this work we have performed Laser Photodetachment Threshold Spectroscopy (LPTS) to determine the electron affinities of the atomic species $^{133}$Cs and $^{16}$O with high precision. The negative ion of Cesium has been produced and investigated at the Gothenburg University Negative Ion and Laser LAboratory (GUNILLA) while the Oxygen anion have been studied in the Double ElectroStatic Ion Ring ExpEriment (DESIREE) at Stockholm University. Pilot studies have also been carried out to measure the electron affinity of complex molecular systems in DESIREE. Specifically, we have studied the beautifully symmetric fullerene C$_{60}^-$ negative ion and its spontaneous and laser induced decays. A preliminary analysis suggests that DESIREE's internal temperature of $\unit{13}{\kelvin}$ may allow an efficient cooling of these initially created hot molecules on time scales of a few seconds. This is a key aspect in measuring detachment thresholds as cooling suppresses hot band contributions associated with vibrationally excited states. Therefore, photodetachment techniques of the types successfully used for atomic species can be implemented for molecules. The preliminary results appear to settle a matter of disagreement in the literature concerning the most precise method to measure the EA of C$_{60}$, that is, LPTS or Photodetachment Electron Spectroscopy (PES).

We present a novel diagnostic technique to probe water vapor (H2O) concentration in hydrogen (H2) combustion environments via the time-resolved measurement of the collisional dephasing of the pure-rotational coherent anti-Stokes Raman scattering (CARS) signal of nitrogen (N2). The rotational Raman coherence of the N2 molecules, induced by the interaction with the pump and Stokes laser fields, dephases on a timescale of hundreds of picoseconds (ps), mostly due to inelastic collisions with other molecules in atmospheric flames. In the spatial region of H2 flames where H2O is present in appreciable amount, it introduces a faster dephasing of the N2 coherence than the other major combustion species do: we use time-resolved femtosecond/picosecond (fs/ps) CARS to deduce the H2O mole fraction from the dephasing effect of its inelastic collisions with N2. The proof-of-principle is demonstrated in a laminar H2/air diffusion flame, performing sequential measurements of the collisional dephasing of the N2 CARS signal up to 360 ps. We measure the temperature and the relative O2/N2 and H2/N2 concentrations at a short probe delay, and input the results in the time-domain model to extract the H2O mole fraction from the signal decay, thus measuring the whole scalar flow fields across the flame front. We furthermore present single-shot simultaneous thermometry and absolute concentration measurements in the turbulent TU Darmstadt/DLR Stuttgart canonical 'H3 flame' performed by dual-probe CARS measurements obtained with a polarization separation approach. This allows us to probe the molecular coherence simultaneously at -20 and -250 ps on the basis of a single-laser-shot, and record the resulting signals in two distinct detection channels of our unique polarization-sensitive coherent imaging spectrometer. The proposed technique allows for measuring the absolute concentrations of all the major species of H2 flames, thus providing a full characterization of the flow composition, as well as of the temperature field.

Brominated organic compounds are toxic ocean-derived trace gases that affect the oxidation capacity of the atmosphere and contribute to its bromine burden. Quantitative spectroscopic detection of these gases is limited by the lack of accurate absorption cross-section data as well as rigorous spectroscopic models. This work presents measurements of high-resolution spectra of dibromomethane, CH2Br2, from 2960 cm−1 to 3120 cm−1 by two optical frequency comb-based methods, Fourier transform spectroscopy and a spatially dispersive method based on a virtually imaged phased array. The integrated absorption cross-sections measured using the two spectrometers are in excellent agreement with each other within 4%. A revisited rovibrational assignment of the measured spectra is introduced, in which the progressions of features are attributed to hot bands rather than different isotopologues as was previously done. Overall, twelve vibrational transitions, four for each of the three isotopologues CH281Br2, CH279Br81Br, and CH279Br2, are assigned. These four vibrational transitions are attributed to the fundamental ν6 band and the nearby nν4 + ν6 − nν4 hot bands (with n = 1–3) due to the population of the low-lying ν4 mode of the Br–C–Br bending vibration at room temperature. The new simulations show very good agreement in intensities with the experiment as predicted by the Boltzmann distribution factor. The spectra of the fundamental and the hot bands show progressions of strong QKa(J) rovibrational sub-clusters. The band heads of these sub-clusters are assigned and fitted to the measured spectra, providing accurate band origins and the rotational constants for the twelve states with an average error of 0.0084 cm−1. A detailed fit of the ν6 band of the CH279Br81Br isotopologue is commenced after assigning 1808 partially resolved rovibrational lines, with the band origin, rotational, and centrifugal constants as fit parameters, resulting in an average error of 0.0011 cm−1.

This master’s thesis explores a space-division-multiplexing (SDM) platform fora delayed-choice experiment. SDM is a multiplexing technique for optical datatransmission that employs spatial modes in a multi- or few-mode fiber to increasethe transmission capacity. The spatial modes can thus be used as separate channels. SDM have shown great potential for quantum information systems, making it intriguing to investigate its broad applications by examining its use in adelayed-choice experiment. The delayed-choice experiment was proposed by J.A.Wheeler in 1978 explored the particle- and wave-like behavior of quantum particles and observe if the particle knows in advance if it should propagate as a waveor a particle through the experimental platform. Hence, it was suggested thatthe experiment should be changed after the particle entered the experimentalplatform. The experiment has afterward been realized in many different constellations but previous wave-particle delayed-choice experiments have not beendemonstrated with SDM nor with an all in fiber platform. The research involved modeling and constructing a SDM fiber-optic platform,only utilizing commercially available fiber optical telecommunication components. The platform was constructed with photonic lanterns, used as spatial division multiplexer and demultiplexer, and a two-input fiber Sagnac Interferometer,as a removable beam splitter. The system was tested with classical light but without difficulties, the platform could move to the quantum domain for performingthe delayed-choice experiment with single photons on the platform. The thesis resulted in a SDM platform with good performance for future measurement of bothparticle- and wave-like behavior of photons in a delayed-choice experiment.

According to Bröstcancer förbundet, mammography is not efficient at detecting tumors in dense breast tissue or diagnosing breast cancer at its early stages. Ultrasound-optical tomography (UOT) is an imaging technique in development and has the potential for deep-tissue imaging. If ultrasound-optical tomography were implemented, it would be easier to differentiate between malignant, benign, and healthy tissue from any type of breast tissue. UOT is an imaging technique that takes advantage of high penetration depth and high spatial resolution of ultrasound imaging and optical imaging. In UOT, a laser light and an ultrasound pulse propagate through the tissue simultaneously at a frequency f$_L$ and f$_{US}$, respectively. The light will scatter while it propagates through the tissue and some of this scattered light will become frequency shifted by ultrasound pulse due to the acousto-optic effect. The tagged light will have the frequency $f_T = f_L + f_{US}$. The tagged (frequency shifted) light can be separated from the untagged light (unshifted light) using a thulium-doped lithium niobate, Tm$^{3+}$:$~$LiNbO$_3$, crystal as a filter. The crystal is kept at a temperature close to zero kelvin because then it exhibits unique characteristics, e.g. it has a narrow linewidth and long-lived hyperfine levels at this temperature. The filter is created by a method known as spectral hole burning (SHB). A laser beam is used to transfer electrons from the ground state to the excited state to create a hole at a specific wavelength. The spectral hole is created at the frequency of the tagged light and hence a narrow bandpass filter is constructed inside the crystal. The tagged light is fully transmitted through the filter while it highly attenuates untagged light. The tagged light is detected with a photodiode and processed in MATLAB after it has been transferred to an oscilloscope. This thesis aims to model and design a phantom probe that minimizes vibration and other unwanted movements or disturbances during measurements. The automated phantom holder will be used for the recording of 3D images. Another task of the thesis was to obtain the absorption spectrum of a 0.005$\%$ Tm$^{3+}$:$~$LiNbO$_3$ crystal when it is cooled down to 3$~$K to ensure that the crystal has the same absorption characteristics as predicted in literature. The absorption line at $\sim$ 800$~$nm is of interest since oxyhemoglobin and deoxyhemoglobin have similar absorption coefficients at $\sim$ 800$~$nm. Optical absorption and scattering information will help determine if the sample contains a cancerous region. The phantom probe was modeled in Solid Works and manufactured through 3D printing. In this setup, the sample holder was chosen to be translated while the ultrasound transducer was stationary to generate less blurry images. The design of the probe has to accommodate two detection schemes, reflection and transmission mode. The phantom probe was automated using a linear servo actuator since it was controlled with pulse-width modulation (PWM). It used a square signal as an input that could be generated with an Arbitrary signal generator (AWG). Using a device that operates with a signal was important because it would make it easier to integrate it into the experimental setup. The whole phantom probe was constructed in a cost-efficient way and in a way that it could be easily incorporated into the experimental setup. The absorption spectrum showed that the crystal has an absorption line at $\sim$ 794.3$~$nm. This absorption spectrum was compared to an absorption spectrum taken at 8$~$K on the same crystal and captured with a different method. Both absorption spectra had the same absorption peaks at almost the same wavelengths but they also showed few discrepancies that may depend on the temperature difference and the recording method. In this thesis, the absorption spectrum data taken was captured by sweeping the wavelength. The signal was captured with a photodiode, transferred to an oscilloscope, and then processed in MATLAB. The absorption spectrum data at 8$~$K was obtained using a Fourier transform spectrometer, resulting in data with little noise and well resolved peaks. To conclude, a functional and robust phantom probe was designed and manufactured that could withstand vibration and other undesired movements. An absorption spectrum of Tm$^{3+}$:$~$LiNbO$_3$ crystal was obtained at 3$~$K and compared to absorption taken at 8$~$K and compared to literature and previous measurements under similar conditions.

An investigation of the radiationless decay of core excited Xe atoms in the region of Xe L3M4,5M4,5 Auger electron kinetic energies (using x-ray energies in the vicinity of the L3 threshold) is presented for Xe adsorbed on Cu, Ag, and Au. The intensity distribution of the decay channels is different compared with Xe in the gas phase. Charge transfer of the core excited electron occurs within tens of attoseconds in all systems for excitation energies approaching the ionization threshold of the condensed system, whereas charge transfer times are substrate-dependent for lower excitation energies. The determination of partial yields into the decay channels allows for the observation of a decay channel present in the Xe/Cu and Xe/Ag systems but not in the case of Xe/Au. Theoretical calculations allow us to interpret this difference as emanating from varying amounts of the ground state hybridization between Xe and the substrates, which impacts the energy of the Auger final states enabling identification of these states giving rise to system specific features in the experimental data.

The broad range of applications for photochemical reactions is the result of light-matter interaction at the electronic level. The diverse application of photochemistry in various fields, including photovoltaic materials, molecular switches, and biological systems are due to electronic and structural transformations induced by photoexcitation as well as molecular alteration due to electron and charge transfer. An improved understanding of these photochemical events is dependent on the fundamental theoretical evaluation, to model and analyze the ultrafast processes. The studies discussed in this thesis explore such theoretical implementation in two different frontiers. In the first study, dynamic simulations are performed to model the light-induced bond dissociation of phenyl azide. The surface hopping formalism, implemented under the semiclassical molecular dynamics approach helped in tracing the time evolution of the electronic and structural levels, involved in the photodissociation. In the second study, the time-dependent density functional theory has been applied to generate XA spectra of imidazole solutions. The theoretical assessments support experimental measurements and provide more insight into the core excitations and structural influence on the absorption spectra. Fotokemiska reaktioner styrs av växelverkan mellan ljus of materia på en elektronisk nivå. I olika fält finns det vitt skilda tillämpningarna av fotokemi. Dessa inkluderar ljusinducerade processer i solceller, molekylära strömbrytare, och biologiska system. Reaktionerna beror av elektroniska och strukturella transformationer som induceras av fotoexcitationen, och kan ge upphov till energi- och laddningsöverföring. För att få utökad förståelse av fotokemiska reaktioner behövs grundläggande teoretiska studier där ultrasnabba processer modelleras och analyseras i jämförelse med experiment. Undersökningar som presenteras i denna avhandling använder sig att teoretiska modeller i två olika områden av fotokemi. I den första studien har vi genomfört dynamiska simuleringar för att modellera ljusinducerad dissociation av fenylazid. Vi have använt en semi-klassisk approximation med hopp mellan olika elektroniska tillstånd vilket gör det möjligt att följa utvecklingen i elektroniska och geometriska frihetsgrader under fotodissociationen. I den andra studien har tidsberoende täthetsfunktionalteori använts för att simulera röntgenabsorptionsspektrum för imidazol i lösning. Genom att utvärdera olika geometriska modeller med teoretiska beräkningar kan vi berika tolkningen av experimentella mätningar, och även få detaljerat insikt i innerskalsexcitationer och hur geometrin påverka röntgenspektrum.

Water has a rich phase diagram with regions of meta-stability, the prime examples being super-cooled and super-heated liquid water.Below ca 50 °C, water exhibits unusual and not yet fully explained anomalous thermodynamic properties upon cooling, for example a minimum in compressibility at 46 °C, a minimum in heat capacity at 35 °C, a density maximum at 4 °C, and a compressibility maximum at -44 °C in the supercooled liquid, at ambient pressure.It is hypothesized that the phase transition (PT) between high- and low-density amorphous ices, below ~120 K, extends toward ambient conditions as a PT between two liquid phases, and ends at a critical point in the deeply supercooled liquid, giving rise to critical fluctuations in density that explain the anomalies.The phase diagram can be examined with molecular dynamics (MD) simulations, where the molecular structure is a direct observable.The realism of a simulation improves with the accuracy of model forces, the number of molecules, and simulated time.Accurate forces can be obtained from wave function (WF) calculations, but the computational demands are high.In computationally efficient models, the accuracy is generally compromised,but with the advent of machine learning, this situation has improved. In this thesis we report on the development of a water model that aims for accuracy similar to the best WF methods, while being efficient enough for predictive MD simulations.Multipole and polarizability tensors have been computed with WF methods for a training set of perturbed water monomers, and fitted with Gaussian process regression as functions of the molecular geometry, in order to create an accurate model of the electrostatic and many-body polarization forces.To obtain accurate short-range forces, due to intermolecular WF overlap, a machine-learning (Gaussian approximation) potential is applied, which is trained on the difference (in forces and energies) between the electrostatic model and an accurate WF method, for a large training-set of water dimers and trimers.To facilitate periodic calculations at constant pressure, the Ewald method and virial stress tensor have been implemented for multipolar forces between flexible molecules.The model shows good agreement with WF calculations of the energies of different test-structures, as well as promising results for thermodynamic properties from MD simulations.

Journal of synchrotron radiation 30(1), 11 - 23 (2023). doi:10.1107/S1600577522009997, With the development of X-ray free-electron lasers (XFELs), producing pulses of femtosecond durations comparable with the coherence times of X-ray fluorescence, it has become possible to observe intensity–intensity correlations due to the interference of emission from independent atoms. This has been used to compare durations of X-ray pulses and to measure the size of a focusedX-ray beam, for example. Here it is shown that it is also possible to observe the interference of fluorescence photons through the measurement of the speckle contrast of angle-resolved fluorescence patterns. Speckle contrast is often used as a measure of the degree of coherence of the incident beam or the fluctuations of the illuminated sample as determined from X-ray diffraction patterns formed by elastic scattering, rather than from fluorescence patterns as addressed here. Commonly used approaches to estimate speckle contrast were found to suffer when applied to XFEL-generated fluorescence patterns due to low photon counts and a significant variation of the excitation pulse energy from shot to shot. A new method to reliably estimate speckle contrast under such conditions, using a weighting scheme, is introduced. The method is demonstrated by comparing the speckle contrast of fluorescence observed with pulses of 3 fs to 15 fs duration., Published by Wiley-Blackwell, [S.l.]

Fragmentation dynamics of core-excited isolated ammonia molecules is studied by two different and complementary experimental methods, high-resolution resonant Auger spectroscopy and electron energy-selected Auger electron–photoion coincidence spectroscopy (AEPICO). The combined use of these two techniques allows obtaining information on different dissociation patterns, in particular fragmentation before relaxation, often called ultrafast dissociation (UFD), and fragmentation after relaxation. The resonant Auger spectra contain the spectral signature of both molecular and fragment final states, and therefore can provide information on all events occurring during the core-hole lifetime, in particular fragmentation before relaxation. Coincidence measurements allow correlating Auger electrons with ionic fragments from the same molecule, and relating the ionic fragments to specific Auger final electronic states, and yield additional information on which final states are dissociative, and which ionic fragments can be produced in timescales either corresponding to the core-hole lifetime or longer. Furthermore, we show that by the combined use of two complementary experimental techniques we are able to identify more electronic states of the NH2+ fragment with respect to the single one already reported in the literature.

Second-order nonlinear optical processes generate radiation across a broad spectrum, including UV and the far-infrared. In this thesis, new light sources in the near(NIR) and mid infrared (MIR) using three-wave mixing geometries in periodically poled potassium titanyl phosphate (PPKTP) is studied. Collinear three-wave mixing is of three types: forward, counter, and backward, defined from propagation directions. Backward mixing is achievable with quasi-phasematching (QPM) - in contrast to birefringent phase matching which only can phasematch co- and counter- propagating geometries. Focus has been on optical parametric oscillators (OPOs), backward wave optical parametric oscillators (BWOPOs), and backward second harmonic generation (BSHG). OPO and BWOPO sources are attractive due to the need for stable, narrowband, and tunable MIR radiation in nanosecond stand-off spectroscopy. The work also pushes the boundaries of nonlinear optics, where lack of efficient sources has limited research on backward processes.Type-0 forward ns-OPOs have broad bandwidth, especially close to degeneracy, due to identical polarization at the parametric wavelengths and moderate dispersion. Probing greenhouse gases, such as CO2, requires narrow bandwidths. Type-2 ns-OPOs with orthogonal polarizations can be used as these have a much-reduced acceptance bandwidth. We provide the design parameters for the QPM grating periodicities in type-2 DFG, and, demonstrate that simple type-2 PPKTP ns-OPOs produce transform-limited mJ pulses with a good beam profile. These type-2 PPKTP OPOs can find use as parametric source for narrowband spectroscopy. Moreover, the type-2 OPOs are also useful for studying other narrow acceptance processes. We used BWOPOs to efficiently generate mJ of nanosecond pulses at 5 kHz repetition rate, corresponding to an average power of 5.65 W, with tunable forward pulses (1-to-1.001 Hz/Hz) and bandwidths ranging from 300 to 400 MHz. A BWOPO bandwidth as small as 274 MHz was obtained when pumped with a high M2 transform-limited laser. We show that the BWOPO is insensitive to temperature variations and is tuned at 2.48 GHz/K. The BWOPO can serve as a pump-tunable spectroscopy source using a single-pass crystal with reduced complexity. From the above, and earlier studies, PPKTP devices are found to be attractive as components for space-borne precision MIR spectroscopy. To study PPKTP's radiation hardness, we conducted experiments, using Type-0 OPO thresholds and transmission spectroscopy, on the long-term changes in linear and nonlinear properties of PPKTP when exposed to low- to mid-energy protons (10 and 60 MeV). The dosages and energies were similar to those in low earth orbit over a five-year period. The results showed no changes in nonlinearity or transmission. We also demonstrated the first efficient, purely backward χ(2) process, i.e., backward second-harmonic generation. The QPM period was Λ = 317 nm. The crystal generated frequency doubled pulses at 1154 nm with an efficiency of 18.7 % and energy of tens of microjoules. A narrowband type-2 ns-OPO was used as pump to measure the temperature bandwidth and confirm the quadratic output/input relationship in the undepleted pump regime. The significant difference in spectral acceptance between BSHG and second harmonic generation (SHG) in PPKTP - calculated to δλBSHG = 53 pm and δλSHG = 13.2 nm, respectively - is confirmed using a ps-BWOPO pump. The temperature tuning was 17.1 pm/K. This work establishes the feasibility of backward optical parametric amplification. We extended our research on potassium titanyl phosphate's (KTP) properties to the infrared and THz region by studying the transmission along the x and y crystallographic axis directions using THz pump-probe spectroscopy in reflection. Finally, backward THz polariton scattering was observed in Type-2 OPOs, along with polariton coupling into THz comb-lines when using an unpoled KTP as an off-axis oscillator. Andra ordningens icke-linjära optiska processer kan ge upphov till elektromagnetisk strålning över ett brett spektrum, inklusive ultraviolett och långvågiga infraröd strålning. Kolinär tre-vågsblandning, kan delas upp i tre olika typer, beroende på fältpropageringsriktningen: framåt, motriktad och bakåt. För att kunna uppnå bakåtgenerering krävs s.k. kvasi-fasmatchning, eftersom dubbelbrytning i naturliga kristaller inte är tillräckligt. I denna studie används kristaller av kaliumtitanylfosfat som dopats med rubidium och sedan polats periodisk (PPKTP, PPRKTP, Rb: PPKTP) för att kunna användas för kvasifasmatchning. I avhandlingen beskrivs hur nya ljuskällor, och olika vågsmixningsgeometrier, har kunnat realiseras med dessa kristaller. Fokus har legat på optiska parametriska oscillatorer (OPO), bakåt-riktade optisk parametriska oscillatorer (BWOPO) och bakåt-riktad frekvensdubbling (BSHG). Dessa ljuskällor är attraktiva då det finns ett stort behov av stabil, smalbandig och avstämbar strålning för bl.a. spektroskopitillämpningar. Resultaten har också flyttat gränsen för vad vi kan åstadkomma med bakåtriktade icke-linjära optiska processer. Konventionella ns-OPO:er av Typ-0 har en bred bandbredd, särskilt nära degenerationspunkten. Detta beror på identisk polarisation hos de parametriska våglängderna och den svaga dispersionen. Tillsammans gör dessa två egenskaper dem mindre användbara för spektroskopiska mätning på växthusgaser där det krävs en smal bandbred, som t.ex. för CO2. För att minska den spektrala acceptansen kan Typ-2 ns-OPO:er med ortogonala polarisationer användas. I avhandlingen presenteras designparametrar för Typ-2 OPOer i PPKTP avseende periodiciteten för QPM-gittret. Vi demonstrerar att enkla Typ-2 OPO:er producerar transform-begränsade pulser med god strålprofil, användbara för smalbandspektroskopi. Dessa OPOer levererade pulser med energier upp till 1.3 mJ och de är också användbara som källa för att studera ickelinjära processer där smal bandbredd är av vikt. Vi konstruerade en BWOPO med nanosekundspulser och pulsenergier på mJ vid en repetitionshastighet på 5 kHz. Framåtpulserna avstämdes med en frekvens på 1 till 1.001 Hz/Hz och dess bandbredd var mellan 300 och 400 MHz. Även när BWOPO pumpades med sämre strålkvalité på lasern (M2 > 4) kunde en bandbredd så liten som 274 MHz mätas. Vidare visade vi att BWOPOn är stabil med avseende på temperaturvariationer, och kunde avstämmas med 2.48 GHz/K. En BWOPO kan då fungera som en spektroskopikälla som kan justeras med pumpfrekvensen. Detta minskar komplexiteten i systemdesignen och möjliggör en enkelpasskristalldesign. PPKTP-kristaller är potentiellt användbara som komponenter i rymdburen precisionsspektroskopi. För att säkerställa att de tål bakgrundsstrålningen i rymden genomförde vi tester av strålningsbeständigheten för PPKTP. Genom att mäta oscillationströskeln för typ-0 OPO:er och transmissionen när PPKTP utsattes för låg till medelhög protonenergi (10 och 60 MeV) kunde vi dra slutsatser om den långsiktiga förändringen. Strålningsdoserna motsvarade de som erhålls för satelliter i låg omloppsbana runt jorden under en femårsperiod. Resultaten visade inga mätbara förändringar i vare sig icke-linjäritet eller transmission. Slutligen demonstrerar vi den första effektiva, rent bakåtriktade χ(2)-processen, med en effektivitet på 18.7 % vid bakåtriktad frekvensdubbling. Här använde vi PPKTP-kristaller med en periodicitet på Λ = 317 nm och genererade µJ-pulser vid 1154 nm. Dessa kunde avstämmas med temperaturen (17.1 pm/K). Vi visade också att det är en stor skillnad i spektral acceptans mellan BSHG och konventionell framåtriktad frekvensdubbling. Vi studerade också KTP:s transmissionsegenskaper i THz-området med hjälp av tidsdomänspektroskopi i reflexion. Bakåtriktad THz polariton-spridning observerades i typ-2 OPO tillsammans med polaritonkoppling i THz-kamlinjer vid användning av en normal icke-polerad KTP som off-axis oscillator. Andreordens ulineære optiske fenomen kan nyttegjøres for produksjon av ett bredt spekter av elektromagnetisk strålning, inkludert dypt infrarødt og ultrafiolett. Trebølge-miksing med parallell geometri kan sammenfattes i tre ulike slag. Fremover, motstående og bakover. For å kunne realisere alle ulike slag kan man bruke kvasifasematching, da dobbeltbrytning ikke er tilstrekkelig for de bakovervendte prossesene. I denne avhandling bruker vi rubidium-dopet kaliumtitanylfosfat med periodisk ferroelektrisk struktur for å kvasifasematche alle de parallelle trebølgemiksingsgeometriene. I oppgaven beskriver vi nye typer lyskilder realisert i kaliumtitanylfosfat. Brorparten av arbeidet dreier seg om, optiske parametriske oscillatorer (OPO), motståenderettede optiske parametriske oscillatorer (BWOPO), og bakovervendt frekvensdobbling (BSHG). Slike eksotiske lyskilder behøves i spektroskopi. Da de kan levere regulerbart lys av liten båndbredde med høy stabilitet. Deler av resultatene i denne avhandling har flyttet grensene for hva som er mulig med ulike geometrier av ulinæroptikk. Type-0 nanosekund OPO’er har normalt en stor båndbredde, spesielt nært degenerasjonspunktet. Dette kommer som følge av identisk polarisasjon hos de parametriske bølgelengdene, og en liten dispersjon. Dessverre skaper dette noen begrensninger for brukbarheten av type-0 ns-OPO’er i spektroskopi, spesielt når man vil gjøre målinger på drivhusgasser som CO2. I slike tilfeller trenger man en liten båndbredde, noe man kan få fra type-2 ns-OPO’er, der de produserte bølgene har ortogonal polarisasjon. I avhandlingen presenterer vi designparametere for den periodiske strukturen i PPKTP som forsterker materiale i type-2 OPO’er. Videre, blir det demonstrert at disse OPO’ene kan produsere transform-begrensede pulser, med god stråleprofil, og er dermed anvendbare for presisjonsspektroskopi. OPO’ene produserer pulser med energier opp mot 1.3 mJ, og kan brukes som lyspumpe for andre ulineære optiske fenomen. Vi produserte en motståenderettet optiskparametriskoscillator med mJ-energi nanosekundpulser og 5 kHz repetisjonhastighet. I denne geometrien, demonstrerer vi for første gang at den fremmadvendte strålen er en regulerbar lyskilde i nanosekund regimet ved hjelp en justerbar laser (1-til-1.001 Hz/Hz). BWOPO strålen har en smal båndbredde mellom 300 til 400 MHz. Vi demonstrerer også at BWOPO kan pumpes med lasere av lavere strålekvalitet (M2 > 4) og samtidig ha en liten båndbredde (274 MHz). BWOPO er demonstrert som en stabil lyskilde lite påvirket av temperaturvariasjoner (2.48 GHz/K). Dette viser at BWOPO’er kan brukes som presise spektroskopi-kilder, justerbar med pumpelaserens bølgelengderegulering. Ettersom lyset passerer PPKTP-krystallen bare én gang i BWOPO-geometrien, er de vesentlig mindre komplisert, sammenlignet med annen lignende teknologi. PPKTP krystaller har den siste tiden blitt mer interessant for bruk i satellitter og romforskning. Dette krever at man måler strålingshardhet til PPKTP. Vi gjennomfører slike tester, ved å bombardere PPKTP krystaller med protoner med energier likt det som finnes ombord i en satellitt med LEO bane rundt jorden (10 og 60 MeV). Dosene tatt opp i PPKTP krystallene er likt det som taes opp i løpet av fem år i bane. Vi bruker terskelverdien for oscillation i ns-OPO’er og linære transmissjonsmålinger før, og etter bombardering, for å måle strålningshardheten. Resultatet viser ingen langvarig forandring, noe som øker interessefaktoren for PPKTP i rombåren forskning. I oppgaven demonstreres den første effektive (18.7 %) rent bakoverrettede χ(2)-prossesen (bakoverettet frekvensdobbling). Her brukte vi PPKTP krystaller med en rekord periodisitet på Λ = 317 nm for å produsere µJ IR-pulser (1154 nm). Man kan variere bølgelengden med temperatur (17.1 pm/K). Vi demonstrerte også de store forskjellene i akseptert spektrum mellom BSHG og normal frekvensdobling. Vi studerte også KTP’s linæere egenskaper i THz-området ved hjelp av tidsdomenespektroskopi i refleksjon. Vi observerte bakoverrettede polaritoner i typ-2 PPKTP ns-OPO’er og brukte polaritonkobling til å produsere THz spektralkammer i en KTP-krystall brukt som skeiv-akse oscillator. QC 2023-05-08

T1ρ is an NMR relaxation mode that is sensitive to low frequency molecular motions, making it an especially valuable tool in biomolecular research. Here, we introduce a new method, SPICY, for measuring T1ρ relaxation times. In contrast to conventional T1ρ experiments, in which the sequence is repeated many times to determine the T1ρ time, the SPICY sequence allows determination of T1ρ within a single scan, shortening the experiment time remarkably. We demonstrate the method using ¹H T1ρ relaxation dispersion experiments. Additionally, we combine the sequence with spatial encoding to produce 1D images in a single scan. We show that T1ρ relaxation times obtained using the single scan approach are in good agreement with those obtained using the traditional experiments.

Laser light absorption is one of the elementary effects of laser material processing. Absorption values are relevant to calculate the process efficiency and predict the impact on the material for the increasingly used laser processes. However, absorption measurement can be a complex task. At high temperatures of metals, only limited experimental data is available due to the dynamic surfaces and the often unknown emissivity needed for the temperature measurement. Models were created to predict the absorption at different temperatures, which are successful with assumptions in some regimes, but often fail in others. For improving the theoretical models, an experimental measurement of high-temperature metal surfaces is desired. Therefore, a radiometric measurement method is proposed in this work using a heating laser to create a metal melt pool, while measuring temperature and reflection of its surface by a second measuring laser beam. General tendencies known from literature could be confirmed by the measurements, while absorption values tend to scatter at increasing temperature. However, trends could be observed. Between melting and boiling temperature, a slight absorption increase was seen in the range between 35% and 38%. Those values indicate that both interband and intraband absorption must be considered to explain the absorption in this regime. At increased temperatures, the intraband absorption becomes the dominating absorption mechanism, reaching absorption values above 45% at very high temperatures. Validerad;2023;Nivå 2;2023-02-13 (joosat);Funder: EIT raw materials, (18079)Licens fulltext: CC BY License

We present a new analytical instrument for studying the optical properties of materials in different gaseous environments at room and controlled elevated temperatures. The system consists of a vacuum chamber, which is equipped with temperature and pressure controllers, a heating band, and a residual gas analyzer and is connected to a gas feeding line via a leak valve. Two transparent view ports located around a sample holder allow for optical transmission and pump-probe spectroscopy using an external optical setup. The capabilities of the setup are demonstrated by conducting two experiments. In the first experiment, we study the photodarkening and bleaching kinetics of photochromic oxygen-containing yttrium hydride thin films illuminated in ultra high-vacuum and correlate it with changes in partial pressures inside the vacuum chamber. In the second study, we investigate changes in the optical properties of a 50 nm V film upon hydrogen absorption.

The orientation of the emissive dipoles in thin-film devices is important since it strongly affects the light outcoupling and thereby the device emission efficiency. The light-emitting electrochemical cell (LEC) is particularly interesting in this context because its emissive dipoles are located in a high electric-field p-n junction, which is formed in situ by redistribution of bulky ions. This implies that the dipole orientation could be distinctly different in the driven LEC compared to the pristine device. This study develops the destructive-interference microcavity method for the accurate in situ determination of the orientation of the emissive dipoles during LEC operation and apply it on a common LEC device comprising an amorphous conjugated polymer termed Super Yellow as the emitter. It is found that ≈95% of the emissive dipoles are oriented in the horizontal direction with respect to the thin-film plane in both the pristine LEC and during steady-state light emission. This finding is attractive since it enables for efficient outcoupling of the generated photons, and interesting because it shows that a horizontal orientation of the emissive dipoles can remain despite the existence of a strong perpendicular electric field and the nearby motion of bulky ions during LEC operation.

International audience; Large aperture periodically-poled Rb:KTP crystals designed for optical parametric amplifiers in 2 µm LIDAR systems were radiation hardness tested by exposure of proton beams at 10 MeV and 60 MeV energies. An irradiation dose of 55 Gy was used to commensurate the crystals' estimated exposure on board a mission in the low-Earth orbit. The irradiation effects were investigated by comparing optical transmission spectra and 2D effective nonlinearity mapping in a 2 µm OPO setup before and after irradiation. The results reveal that the periodically poled structure remained intact after irradiation, and the changes in the optical transmission and nonlinear properties were close to the measurement uncertainty. This investigation is essential for realizing efficient frequency converters for space applications, such as spaceborne active greenhouse gas monitoring LIDAR instruments or correlated photon-pair sources.

The research presented in this thesis covers a wide range of applications for, and integrations of, a stripline split-ring resonator (SSRR) microplasma source. Common throughout the presented works is the always present, but sometimes secondary, focus on analyzing the light and matter that is emitted as gas is flowed through theplasma of the SSRR. When evaluated as a heater in a cold-gas microthruster intended for attitude adjustment and orbit maintenance of miniaturized satellites, the plasma was shown to be a more efficient than two modes of resistive heating in improving the specific impulse of the thruster. Furthermore, the ionized exhaust plume of the thruster was used to derive a novel method of estimating its efficiency. In further analysis of the plasma parameters, correlations between supplied power, ion density, and thrust efficiency were uncovered and verified by Langmuir probe measurements. In subsequent experiments, the use of the SSRR as a residual gas analyzer was explored, first by comparing different classes of regression methods for determining gas species concentrations from emitted UV-NIR spectra from the plasma. In a second study, the wide range spectrometer was replaced with an optical filter and a photodetector, in a differential gas sensor setup where the regression methods were replaced with peak intensity differentiation. With the SSRR’s prospects as a gas sensor confirmed, further work focused on integrating it in a transcutaneous blood gas monitoring (TBM) system. To address the shortcomings of existing systems, a series of three studies covered the fabrication and evaluation of (i) A soft gas-collecting patch that, with its accompanying microfluidics, transported the gas that permeates the skin to the sensor, (ii) A novel fabrication technique to integrate an electrical interface in the bulk of the patch, and a prototype out-of-plane skin heater, and (iii) A theoretical model that related the transcutaneous gas composition to blood gas concentration based on a computational fluid dynamics model. Finally, the sensor and gas collector were integrated in a fully functional TBM system. In conclusion, the thesis explores the use of an SSRR throughout the three cornerstone configurations of microsystem technology: as an actuator for microsatellite propulsion, as a sensor for gas measurements, and integrated in a system for blood gas monitoring.

We present an in-situ and real-time investigation of the formation of YHO and GdHO thin films grown by reactive e(-)-beam evaporation. Mass changes were continuously monitored during deposition, oxidation, and illumination using a highly sensitive quartz crystal microbalance, while changes in chemical composition and depth profiles were investigated simultaneously by ion beam analysis. Results highlight the strong reactivity of freshly deposited YHx and GdHx films, even under ultra-high vacuum conditions. Oxidation starts at the surfaces of the films and the oxidation rate is strongly dependent on the O-2 pressure. The response of the system under ion beam irradiation and in-situ illumination is also presented and discussed. For the measured mass changes, a quantitative agreement better than 2% was observed between both techniques and demonstrates the consistency and sensitivity of this approach.

The Tandem Laboratory at Uppsala University, a national research infrastructure forworld-leading materials analysis, has a long history of performing hydrogen measurementusing NRA (Nuclear Reaction Analysis). This project intents to diversify the infras-tructure for hydrogen measurement by investigating the feasibility of an advanced ERCS(Elastic Recoil Coincidence Scattering) system, enabling finer detection limits. The sys-tem, based on a DSSD (Double-sided Silicon Strip Detector) and a 64 channel dataacquisition system, is set up, tested and calibrated using both single- and triple peakα-radiation sources. Results indicate that all but 14 front segments work correctly. Thestatus of three segments could not be determined due to faulty pre-amplifier channels.Two of the segment faults were found to be caused by snapped electrode connections onthe DSSD. The status of half the backside rings could not be determined due to a faultypre-amplifier. Despite this, the energy spectrum of a 241Am α-particle source was mea-sured with good resolution, showing a clear energy peak corresponding to the 5486 keVα-particles with FWHM equaling 270 keV. Calculations indicate an average dead timefor the working channels of 1.37 %. Measurements on a 239Pu-241Am-244Cm α-particlesource resulted in three main peaks with energies at 5155 keV, 5486 keV and 5805 keV,corresponding to the three peaks of the α-source. Results indicated FWHMs of 208 keV,190 keV and 169 keV respectively, with an average dead time of 32.8 %. These resultsdemonstrate that the detector is in working condition. Furthermore, the pre-amplifiershave been examined and any dead channels are accounted for.

The main goal of the GBAR (Graviational Behaviour of Antihydrogen at Rest) experiment is to investigatethe gravitational effect on antimatter by measuring the classical free fall of an antihydrogen atom. The requiredpositrons are created by pair production inside a tungsten target and are moderated using a tungsten mesh. In thisthesis, two schemes are examined to determine the feasibility of replacing the tungsten moderator with a solid neonmoderator which would increase the moderation efficiency from η+,W ≈ 10−3 to η+,Ne ≈ 10−2. For the first scheme,the moderator is placed directly behind the target. We determined the power deposition inside the moderator tobe approximately 60 W which is at least one order of magnitude larger than the available cooling power to keep theneon at the required temperature. For the second scheme, a combination of magnetic fields is applied to separatethe electrons from the positrons before hitting the moderator. The field configuration was optimized leading to 11%to 16% of positrons hitting the moderator that have mostly small kinetic energies. Finally, an energy consideringscoring function was developed which values slow positrons higher and the relevant magnetic fields were optimizedwith respect to reaching the maximal score.

Plasmonic effects in nanosized particles enhance the interaction between light and matter due to the localized surface plasmon resonance, with potential applications such as all-optical transistors and optical computers. Commonly, the dynamics of nanoparticles’ optical properties are assessed via pump-probe spectroscopy, where a plasmonic structure is exited by an initial laser, the pump. Thereafter a second, less intense laser, a probe, interacts with the now excited structure at a time delay. Through measurements of the probelight transmitted by the matter, the optical dynamics of the structure are monitored. Similar methodologies can potentially be used for other applications as well, such as all-optical switching. This study focuses on an implementation of a numerical finite element method model simulating a pump-probe experiment to predict the effects of different geometries and evaluate experimental data. The simulations are split into three parts. Initially, periodically spaced nanoparticles are excited by the pump laser. Then the model estimates the internal thermal dynamics of the excited nanoparticles and in turn, determines the change in complex permittivity. Lastly, the probe-matter interaction is modeled. To evaluate the model, a comparison with another model was performed. Furthermore, simulations of periodically spaced gold dimer nanoparticles in air were done to investigate how dimers affect transmitted light. For a probe light polarization rotated 45◦ against the axis parallel to the dimer, a change in rotation of 6◦ over 35 fs was induced by the pump, indicating a potential switching mechanism.

We present a new design of a robust cavity-enhanced frequency comb-based spectrometer operating under the continuous-filtering Vernier principle. The spectrometer is based on a compact femtosecond Er-doped fiber laser, a medium finesse cavity, a diffraction grating, a custom-made moving aperture, and two photodetectors. The new design removes the requirement for high-bandwidth active stabilization present in the previous implementations of the technique, and allows scan rates up to 100 Hz. We demonstrate the spectrometer performance over a wide spectral range by detecting CO2 around 1575 nm (1.7 THz bandwidth and 6 GHz resolution) and CH4 around 1650 nm (2.7 THz bandwidth and 13 GHz resolution). We achieve absorption sensitivity of 5 × 10−9 cm-1 Hz-1/2 at 1575 nm, and 1 × 10−7 cm-1 Hz-1/2 cm-1 at 1650 nm. We discuss the influence of the scanning speed above the adiabatic limit on the amplitude of the absorption signal.

Physical review / E 107(1), 015205 (2023). doi:10.1103/PhysRevE.107.015205, Saturable absorption is a nonlinear effect where a material’s ability to absorb light is frustrated due to a high influx of photons and the creation of electron vacancies. Experimentally induced saturable absorption in copper revealed a reduction in the temporal duration of transmitted X-ray laser pulses, but a detailed account of changes in opacity and emergence of resonances is still missing. In this computational work, we employ non-local thermodynamic equilibrium plasma simulations to study the interaction of femtosecond X-rays and copper. Following the onset of frustrated absorption, we find that a K–M resonant transition occurring at highly charged states turns copper opaque again. The changes in absorption generate a transient transparent window responsible for the shortened transmission signal. We also propose using fluorescence induced by the incident beam as an alternative source to achieve shorter X-ray pulses. Intense femtosecond X-rays are valuable to probe the structure and dynamics of biological samples or to reach extreme states of matter. Shortened pulses could be relevant for emerging imaging techniques., Published by Inst., Woodbury, NY

Magneto-optical (MO) effects, viz. magnetically induced changes in light intensity or polarization upon reflection from or transmission through a magnetic sample, were discovered over a century and a half ago. Initially they played a crucially relevant role in unveiling the fundamentals of electromagnetism and quantum mechanics. A more broad-based relevance and wide-spread use of MO methods, however, remained quite limited until the 1960s due to a lack of suitable, reliable and easy-to-operate light sources. The advent of Laser technology and the availability of other novel light sources led to an enormous expansion of MO measurement techniques and applications that continues to this day (see section 1). The here-assembled roadmap article is intended to provide a meaningful survey over many of the most relevant recent developments, advances, and emerging research directions in a rather condensed form, so that readers can easily access a significant overview about this very dynamic research field. While light source technology and other experimental developments were crucial in the establishment of today's magneto-optics, progress also relies on an ever-increasing theoretical understanding of MO effects from a quantum mechanical perspective (see section 2), as well as using electromagnetic theory and modelling approaches (see section 3) to enable quantitatively reliable predictions for ever more complex materials, metamaterials, and device geometries. The latest advances in established MO methodologies and especially the utilization of the MO Kerr effect (MOKE) are presented in sections 4 (MOKE spectroscopy), 5 (higher order MOKE effects), 6 (MOKE microscopy), 8 (high sensitivity MOKE), 9 (generalized MO ellipsometry), and 20 (Cotton-Mouton effect in two-dimensional materials). In addition, MO effects are now being investigated and utilized in spectral ranges, to which they originally seemed completely foreign, as those of synchrotron radiation x-rays (see section 14 on three-dimensional magnetic characterization and section 16 on light beams carrying orbital angular momentum) and, very recently, the terahertz (THz) regime (see section 18 on THz MOKE and section 19 on THz ellipsometry for electron paramagnetic resonance detection). Magneto-optics also demonstrates its strength in a unique way when combined with femtosecond laser pulses (see section 10 on ultrafast MOKE and section 15 on magneto-optics using x-ray free electron lasers), facilitating the very active field of time-resolved MO spectroscopy that enables investigations of phenomena like spin relaxation of non-equilibrium photoexcited carriers, transient modifications of ferromagnetic order, and photo-induced dynamic phase transitions, to name a few. Recent progress in nanoscience and nanotechnology, which is intimately linked to the achieved impressive ability to reliably fabricate materials and functional structures at the nanoscale, now enables the exploitation of strongly enhanced MO effects induced by light-matter interaction at the nanoscale (see section 12 on magnetoplasmonics and section 13 on MO metasurfaces). MO effects are also at the very heart of powerful magnetic characterization techniques like Brillouin light scattering and time-resolved pump-probe measurements for the study of spin waves (see section 7), their interactions with acoustic waves (see section 11), and ultra-sensitive magnetic field sensing applications based on nitrogen-vacancy centres in diamond (see section 17)., Despite our best attempt to represent the field of magneto-optics accurately and do justice to all its novel developments and its diversity, the research area is so extensive and active that there remains great latitude in deciding what to include in an article of this sort, which in turn means that some areas might not be adequately represented here. However, we feel that the 20 sections that form this 2022 magneto-optics roadmap article, each written by experts in the field and addressing a specific subject on only two pages, provide an accurate snapshot of where this research field stands today. Correspondingly, it should act as a valuable reference point and guideline for emerging research directions in modern magneto-optics, as well as illustrate the directions this research field might take in the foreseeable future., Journal of Physics D: Applied Physics, 55 (46), ISSN:0022-3727, ISSN:1361-6463

Vortex phase masks have been shown to be an efficient means to reduce the blinding stellar light in high-contrast imaging instruments. Once placed at the focal plane of the telescope, the helical phase ramp of a vortex phase mask diffracts the light of a bright on-axis source outside the re-imaged telescope pupil, while transmitting the light of a faint off-axis companion nearly unaffected. The Annular Groove Phase Mask (AGPM) is a broadband metasurface implementation of a vector vortex phase mask using the artificial birefringence of a circular subwavelength grating etched onto a diamond substrate. To date, the AGPM design has been optimized using rigorous coupled-wave analysis (RCWA), which is a valid tool to simulate periodic straight gratings. However, we have now reached a performance level where the curvature of the grating lines at the center becomes a limiting factor. Here, we use a finite-difference time-domain (FDTD) method to correctly describe the AGPM performance, including the effect of the curved grating close to its center. We confirm the validity of this simulation framework by comparing its predictions with experimental results obtained on our infrared coronagraphic test bench, and we show that RCWA fails at reproducing correctly the central AGPM performance, confirming the need for a full 3d simulation tool such as FDTD. Finally, we use FDTD to optimize the grating parameters at the AGPM center, and conclude with a new optimal design.

A three-level system can be used in a $\Lambda$-type configuration in order to construct a universal set of quantum gates through the use of non-Abelian non-adiabatic geometrical phases. Such construction allows for high-speed operation times which diminish the effects of decoherence. This might be, however, accompanied by a breakdown of the validity of the rotating wave approximation (RWA) due to the comparable time scale between counter-rotating terms and the pulse length, which greatly affects the dynamics. Here, we investigate the trade-off between dissipative effects and the RWA validity, obtaining the optimal regime for the operation of the holonomic quantum gates., Comment: 8 pages, 6 figures

A transportable refractometer for assessment of kPa pressures with ppm level precision is presented. It is based on the GAs MOdulation Refractometry (GAMOR) methodology, making it resistant to fluctuations and drifts. At the National Metrology Institute at RISE, Sweden, the system assessed pressures in the 4.3 - 8.7 kPa range with sub-ppm precision (0.5 - 0.9 ppm). The system was thereafter disassembled, packed, and transported 1040 km to Umea University, where it, after unpacking and reassembling, demonstrated a similar precision (0.8 - 2.1 ppm). This shows that the system can be disassembled, packed, transported, unpacked, and reassembled with virtually unchanged performance.

For many applications of extreme ultraviolet (XUV) and x-ray pulses a small focus size is crucial to reach the required intensity or spatial resolution. In this article, we present a simple way to characterize an XUV focus with a resolution of 1.85 micrometer. Furthermore, this technique is applied for the measurement and optimization of the focus of an ellipsoidal mirror for photon energies ranging from 18 to 150 eV generated by high-order harmonics. We envisage a broad range of applications of this approach with sub-micrometer resolution from high-harmonic sources via synchrotrons to free-electron lasers., 9 pages, 6 figures

We use a Fourier transform spectrometer based on a difference frequency generation optical frequency comb to measure high-resolution, low-pressure, room-temperature spectra of methane in the 1250 - 1380 cm$^{-1}$ range. From these spectra, we retrieve line positions and intensities of 678 lines of two isotopologues: 157 lines from the $^{12}$CH${_4}$ ${\nu}$${_4}$ fundamental band, 131 lines from the $^{13}$CH${_4}$ ${\nu}$${_4}$ fundamental band, as well as 390 lines from two $^{12}$CH${_4}$ hot bands, ${\nu}$${_2}$ + ${\nu}$${_4}$ - ${\nu}$${_2}$ and 2${\nu}$${_4}$ - ${\nu}$${_4}$. For another 165 lines from the $^{12}$CH${_4}$ ${\nu}$${_4}$ fundamental band we retrieve line positions only. The uncertainties of the line positions range from 0.19 to 2.3 MHz, and their median value is reduced by a factor of 18 and 59 compared to the previously available data for the $^{12}$CH${_4}$ fundamental and hot bands, respectively, obtained from conventional FTIR absorption measurements. The new line positions are included in the global models of the spectrum of both methane isotopologues, and the fit residuals are reduced by a factor of 8 compared to previous absorption data, and 20 compared to emission data. The experimental line intensities have relative uncertainties in the range of 1.5 - 7.7%, similar to those in the previously available data; 235 new $^{12}$CH${_4}$ line intensities are included in the global model.

In the context of quantum technologies over continuous variables, Gaussian states and operations are typically regarded as freely available, as they are relatively easily accessible experimentally. In contrast, the generation of non-Gaussian states, as well as the implementation of non-Gaussian operations, pose significant challenges. This divide has motivated the introduction of resource theories of non-Gaussianity. As for any resource theory, it is of practical relevance to identify free conversion protocols between resources, namely, Gaussian conversion protocols between non-Gaussian states. Via systematic numerical investigations, we address the approximate conversion between experimentally relevant single-mode non-Gaussian states via arbitrary deterministic one-to-one mode Gaussian maps. First we show that cat and binomial states are approximately equivalent for finite energy, while this equivalence was previously known only in the infinite-energy limit. Then we consider the generation of cat states from photon-added and photon-subtracted squeezed states, improving over known schemes by introducing additional squeezing operations. The numerical tools that we develop also allow one to devise conversions of trisqueezed into cubic-phase states beyond previously reported performances. Finally, we identify various other conversions which instead are not viable.

A theoretical overview of the core-to-core (3d-4f) resonant inelastic X-ray scattering (RIXS) spectra of actinide dioxides AnO2 (An = Th, U, Np, Pu, Am, Cu, Bk, Cf) is provided. The 3d-4f RIXS maps were calculated using crystal-field multiplet theory and turned out to be significantly different at the An M5 vs M4 edges, because of selection rules and final state effects. The results of the calculations allowed for a general analysis of so-called high-energy-resolution fluorescence-detected X-ray absorption (HERFD-XAS) spectra. The cuts of the calculated RIXS maps along the incident energy axis at the constant emitted energy, corresponding to the maximum of the RIXS intensity, represented the HERFD spectra and provided their comparison with calculated conventional X-ray absorption (XAS) spectra with a reduced core-hole lifetime broadening at the An M5 and M4 edges. Although the An M5 HERFD profiles were found to depart from the X-ray absorption cross-section, in terms of appearing additional transitions, the results of calculations for the An M4 edges demonstrate overall better agreement between the HERFD and XAS spectra for most dioxides, keeping in mind a restricted HERFD resolution, because of the core–hole lifetime broadening in the final state. The results confirm the utility of HERFD for the An chemical state determination and indicate the importance of calculating the entire RIXS process in order to interpret the HERFD data correctly., A theoretical overview of the core-to-core resonant inelastic X-ray scattering of actinide dioxides is provided using crystal-field multiplet theory. The calculations allowed for a general analysis of high-energy-resolution fluorescence-detected X-ray absorption (HERFD-XAS) spectra and their comparison with conventional XAS.

Significance: Tissue simulating phantoms are an important part of validating biomedical optical techniques. Tissue pathology in inflammation and oedema involves changes in both water and hemoglobin fractions. Aim: We present a method to create solid gelatin-based phantoms mimicking inflammation and oedema with adjustable water and hemoglobin fractions. Approach: One store-bought gelatin and one research grade gelatin were evaluated. Different water fractions were obtained by varying the water-to-gelatin ratio. Ferrous stabilized human hemoglobin or whole human blood was added as absorbers, and the stability and characteristics of each were compared. Intralipid® was used as the scatterer. All phantoms were characterized using spatial frequency domain spectroscopy. Results: The estimated water fraction varied linearly with expected values (R2 = 0.96 for the store-bought gelatin and R2 = 0.99 for the research grade gelatin). Phantoms including ferrous stabilized hemoglobin stayed stable up to one day but had methemoglobin present at day 0. The phantoms with whole blood remained stable up to 3 days using the store-bought gelatin. Conclusions: A range of physiological relevant water fractions was obtained for both gelatin types, with the stability of the phantoms including hemoglobin differing between the gelatin type and hemoglobin preparation. These low-cost phantoms can incorporate other water-based chromophores and be fabricated as thin sheets to form multilayered structures. Funding: This research was financially supported by Knut and Alice Wallenberg Foundation’s Center for Molecular Medicine at Linkoping University (WCMM) and Hudfonden’s Edvard Welander och Finsenstiftelsen.