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Condensation of hydrogen Rydberg atoms (highly electronically excited) into the lowest energy state of condensed hydrogen i.e. the ultra-dense hydrogen phase, H(0), has gained increased attention not only from the fundamental aspects but also from the applied point of view. The physical properties of ultra-dense hydrogen H(0) were recently reviewed (Physica Scripta 2019 https://doi.org/10.1088/1402-4896/ab1276 ), summarizing the results reported in 50 publications during the last ten years. The main application of H(0) so far is as the fuel and working medium in nuclear particle generators and nuclear fusion reactors which are under commercial development. The first fusion process showing sustained operation above break-even was published in 2015 (AIP Advances) and used ultra-dense deuterium D(0) as fuel. The first generator giving a high-intensity muon flux intended for muon-catalyzed fusion reactors was patented in 2017, using H(0) as the working medium. Here, we first focus on the different nuclear processes using hydrogen isotopes for energy generation, and then on the detailed processes of formation of H(0). The production of H(0) employs heterogeneous catalysts which are active in hydrogen transfer reactions. Iron oxide-based, alkali promoted catalysts function well, but also platinum group metals and carbon surfaces are active in this process. The clusters of highly excited Rydberg hydrogen atoms H(l) are formed upon interaction with alkali Rydberg matter. The final conversion step from ordinary hydrogen Rydberg matter H(l) to H(0) is spontaneous and does not require a solid surface. It is concluded that the exact choice of catalyst is not very important. It is also concluded that the crucial feature of the catalyst is to provide excited alkali atoms at a sufficiently high surface density and in this way enabling formation and desorption of H(0) clusters. Finally, the relation to industrial catalytic processes which use H(0) formation catalysts is described and some important consequences like the muon and neutron radiation from H(0) are discussed.

The main chemical reactions that lead to formation of the nonequilibrium two-temperature plasma and highly excited Rydberg complexes are considered. A special attention is given to l-mixing reaction responsible for the formation of quantum resonance properties for radio wave propagation medium. A detailed analysis of the influence of Rydberg states to the behavior of GPS signals in D and E layers of the ionosphere is presented. It is shown that the transition frequencies between the excited states of orbitally degenerate Rydberg complex are resonant with respect to the carrier frequencies of GPS. That is why these states are the main cause of the GPS signal distortion. The mechanism of GPS signal delay in D and E layers is also discussed.

CIS(D∞) method provides reasonable valence excitation energies, but fails for Rydberg states. A corrected CIS(D∞) method is proposed where excitation energies are calculated based on the energy expression in EOM-CCSD(2) using wavefunctions from CIS(D∞). Its performance on singlet and triplet valence and Rydberg excitation energies is investigated by comparing with CC3 results. Excitation energies with this method are always overcorrected. On the other hand, reasonable valence and Rydberg excitation energies will be achieved when the energy correction is halved. This method has a non-iterative N6 scaling and can serve as an economical method in studying both valence and Rydberg excitations.

In this work we report very accurate variational calculations of the twelve lowest 2 S Rydberg states of the lithium atom performed with the finite-nuclear-mass (FNM) approach and with all-electron explicitly correlated Gaussian functions. The FNM non-relativistic variational energies of the states are augmented with the leading relativistic and QED corrections. The calculated transition energies are compared with the previous works (only eight states of the series were calculated before) and with the available experimental results. Density distributions of the electrons and the nucleus in the center-of-mass frame are also shown.

Thirty eight doublet electronic states of the Rydberg molecule NaHe are studied by means of numerical solution of the Schrodinger equation using the finite element method. Twelve of these 38 electronic states are studied for the first time. It is confirmed that potential-energy curves (PECs) of high Rydberg Σ–states have several wells and barriers at large internuclear distances due to radial oscillations of the electron density in the Rydberg states of the sodium atom.

We consider the cascade neutralization of highly charged ions in the interaction with metal-dielectric film surface at moderate ionic velocities and arbitrary angle of incidence. We use the recently developed micro-staircase model based on the quasi-resonant two-state vector model to obtain the final ionic charge in front of the metal surface and calculate the corresponding neutralization energy. Within the framework of the model, the electrons are captured from the metal into the particular ionic Rydberg states inside the dielectric. We discuss the interplay of the collision geometry and surface parameters in the neutralization process for the ArZ+, KrZ+ and XeZ+ ions. It is demonstrated that the equal neutralization energies can be achieved for different combinations of the angles of incidence and dielectric constants of the film. From the equi-neutralization curves we examine the film properties for the particular collision geometry, for which the neutralization energy (together with the deposited kinetic energy) is sufficient for the formation of the surface nanostructure (crater) of a given size. The corresponding threshold values of the dielectric constants are recognized.

Large-scale four-component relativistic calculations have been carried out for excited states of the tris-(allyl)-iridium complex, Ir(C3H5)3, using the relativistic polarization propagator method. The main focus was on providing insight into the lowest excited states of the three different structural forms of the complex, C3, C3h, and C1, including prediction of the excitation spectra and elucidation of spin-orbit coupling (SOC) effects for these forms. To unravel SOC effects, results of spin-orbit (SO) calculations were contrasted to results of spin-free (SF) calculations. Both the SO and SF calculations predict the lowest excited states of all three forms are of Rydberg type. We identified several Rydberg series, characterized by different hole configurations, that constitute the low-energy parts of the SO and SF excitation spectra. The SO spectra, however, differ notably from the corresponding SF spectra, pointing out to the influence of SOC. The most pronounced differences are observed for the SO and SF spectra of the C3h form. Our analysis indicates that SOC in this form causes strong alterations of the frontier occupied orbitals, participating in the excitations. As a result, excited states belonging to the first two Rydberg series are characterized by different electronic structure (hole configurations) in the SO and SF cases. Besides the orbital alteration effect, two other SOC effects, zero-field splitting and singlet-triplet mixing were identified in the SO spectra of all three forms. These effects result in new lines in the SO spectra and notable redistribution of the spectral intensity.

Accurate high lying resonance energies of the (3d94s 3D3,2,1)np and the (3d94s 1D2)np (n = 5–40) Rydberg series originating from the (3d104s 1S1/) ground state of the Cu-like Zn+ ion are reported. Calculations are performed in the framework of the Screening Constant by Unit Nuclear Charge (SCUNC) formalism. The results obtained compared very well with high resolution ALS measurements along with DARC, Dirac Atomic R-matrix Codes computations [Hinojoha et al., MNRAS, 470, 4048 (2017)]. Analysis of the present results is achieved in the framework of the standard quantum-defect theory and of the SCUNC-procedure based on the calculation of the effective charge. It is demonstrated that the SCUNC-method can be used to assist fruitfully experiments for identifying narrow resonance energies due to overlapping peaks New high lying accurate resonance energies (n = 16–40) are tabulated as benchmarked data for interpreting spectra from this trans-Fe element in astrophysical objects.

Excited-state energy levels for quartet states 1s22l2l′nl″ (n=2–7; l=s, p; l′=s, p; l″=s, p, d, f) pertaining to 4Le,o (m) (L=S, P, D; m=1–5) Rydberg series in Si9+ ion are studied, using multi-configuration Rayleigh-Ritz variation method. Corrections for the relativistic effects, mass polarization effect, and quantum electrodynamics (QED) effect are taken into account to obtain the accurate relativistic energies. Transition probabilities, line strengths, oscillator strengths, and wavelengths of electric-dipole transitions between these quartet states are systematically calculated and compared with available reference data. These calculated data could be used for the identification of spectral lines arising from the coronal atmospheres and experimental study in future work.

We present the amb i t software package for general atomic structure calculations. This software implements particle–hole configuration interaction with many-body perturbation theory (CI+MBPT) for fully relativistic calculations of atomic energy levels , electric- and magnetic-multipole transition matrix elements, g-factors and isotope shifts . New numerical methods and modern high-performance computing techniques employed by this software allow for the calculation of open-shell systems with many valence-electrons ( N ≥ 5 ) to a high degree of accuracy and in a highly computationally efficient manner. Program summary Program Title: amb i t Program Files doi: http://dx.doi.org/10.17632/7xfxhr9mg6.1 Licensing provisions: GPLv3 Programming language: C++11 Nature of problem: Calculation of atomic/ionic spectra, including energy levels, electric and magnetic multipole transition matrix elements, and isotope shifts. Solution method: The programme calculates energy levels and wavefunctions using either configuration interaction (CI) only, or CI with many-body perturbation theory (CI+MBPT) in the Brillouin–Wigner MBPT formalism. Restrictions: The programme is not designed to treat highly-excited (Rydberg) states or continuum processes to a high degree of accuracy. Additional comments: Programme github repository

The threshold photoelectron spectra of SO2 were recorded over the photon energy range (12–50 eV) under high-resolution conditions using synchrotron radiation. Extensive vibrational ‘filling-in’ is found in the Franck-Condon gap regions between the three lowest ionic-state band systems that is attributed to autoionization of Rydberg states lying in these regions. The outer-valence ionization region (12–18 eV) consists mainly of the vibrationally well-defined electronic states of ( X ˜ 2A1), ( A ˜ 2B2), ( B ˜ 2A2), ( C ˜ 2B1), ( D ˜ 2A1) and ( E ˜ 2B2) being derived from the molecular orbitals: (8a1), (5b2), (1a2), (2b1), (7a1) and (4b2), respectively, but there are also some features that can be associated with the two weak satellite structures (1 2B1) and ( 3 B 2 2 ). On the other hand, in the inner-valence ionization region (18–50 eV) the opposite is true, i.e., a well-defined electronic state structure is limited to the ( F ˜ 2A1) state of SO2+ with a (6a1) molecular orbital origin, with the preponderance of the remaining structure due to broad satellite features involving ionization from the inner-valence (3b2) and (5a1) molecular orbitals.

The nature and energies of the low-lying electronic excited states of vanadium and chromium cycloheptatrienyl cyclopentadienyl complexes are determined on the basis of time-dependent density functional theory (TD DFT) calculations compared with the experimental gas-phase and condensed-phase absorption spectra. Both intravalency and Rydberg electronic excitations are taken into account. It is demonstrated that TD DFT can predict correctly the absorption band positions and describe well the influence of the metal atom and the ligand on the electronic transition energies. On the basis of comparison with the experimental transition energies the best combinations of the functional and basis set are chosen. For the mixed sandwiches, the “pure” BPW91 and hybrid B3LYP functionals are found to perform much better than the range-separated CAM-B3LYP and WB97XD functionals. The TD DFT calculations suggest new assignments for the Rydberg 4d peak in the gas-phase spectrum of the chromium complex and for the long-wavelength absorption band in the solution spectrum of the vanadium derivative.

We present a theoretical study on probe field propagation through a three-level Ξ type system formed in an atomic vapour medium in presence of a strong control field. The model is based on density matrix method and is solved analytically, without neglecting any term in any power of probe and control Rabi frequencies, to find out the probe response under Doppler free condition as well as at room temperature. The probe response for a four-level Ξ type system is also determined analytically. Electromagnetically induced transparency is formed in the simulated probe response for both the level schemes. We also present the switching of probe field propagation from subluminal to superluminal as a function of probe detuning for different control transitions, one of which is to a Rydberg state. The switching window becomes asymmetric under detuned control field with the asymmetry depending on the wavelength mismatching factor between the control field and the probe field. Under strong probe regime probe propagation switches from superluminal to subluminal on resonance when the wavelength mismatch between the probe and the control field is increased, an effect which can be explained with the help of the analytical model that is free from any perturbative treatment.

To study quantum dynamics in the non-relativistic regime, the standard practice is to use non-relativistic quantum mechanics, instead of the relativistic theory, because it is thought the approximate non-relativistic result is always close to the relativistic one. Here we present a theoretical argument that this expectation is not true in general. In addition, supporting numerical evidence for the free rotor and hydrogen atom also shows the agreement between the two theories can break down quickly. For the radial Rydberg wave packet in hydrogen atom, the breakdown can occur before spontaneous emission and thus could be tested experimentally. Our surprising result shows relativistic quantum mechanics must be used, instead of the approximate non-relativistic theory, to correctly study quantum dynamics in the non-relativistic regime after the breakdown time. This paradigm shift opens a new avenue of research in a wide range of fields from atomic to molecular, chemical and condensed-matter physics.

We report the regularity of experimental evolution of Rydberg six-wave mixing (SWM) spatial images that were effectively controlled by adjusting various probe field parameters. Due to the high-order nonlinear Rydberg process, evolution of the spatial defocusing and splitting was observed by changing the detuning, polarization, and power of the probe field. Modulated spatial images obtained in a Rydberg nonlinear medium were found to be related to the refractive index. This study clarifies the spatial transmission rules for Rydberg SWM, which can be used to study the light field modulation of space imaging of a Rydberg atom ensemble and can provide evidence for the design of advanced materials.

Photoabsorption spectra of isoflurane and sevoflurane have been measured with synchrotron radiation over the photon range 5.0–10.8 eV. Low-lying excited singlet valence and Rydberg states are investigated and the assignments supported by quantum chemical calculations, the latter also helping to identify the triplet states. This provides the first comprehensive investigation of all excited electronic states up to the first ionisation energy. The Rydberg series converging to the ionisation energy limits are identified according to the magnitude of the quantum defects. The measured absolute cross-sections have been used to calculate the photolysis lifetimes of isoflurane and sevoflurane in the Earth’s atmosphere.

International Journal of Mass Spectrometry, 435, ISSN:1387-3806, ISSN:1873-2798

The 1+1 REMPI spectrum of SiO in the 210–220 nm range was recorded. Observed bands were mostly assigned to the vibrational bands v ″ = 0 - 3 , v ′ = 5 - 10 of the A - X electronic transition. Additionally, a band near 216–217 nm was tentatively assigned as a 2-photon transition from X to the n = 12 , 13 [ X 2 Σ + , v + = 1 ] Rydberg states. Based on observed lines we estimated the IP of SiO to be 11.594(5) eV. The SiO+ cation has previously been identified as having a cycling transition useful for state control by optical pumping. Our work allowed us to identify an efficient method for loading an ion trap with rotationally and vibrationally cold SiO+ from an ablated sample of SiO by photoionizing through the (5,0) A - X band at 213.977 nm.

Quantum communication with terahertz (THz) frequency signals has many advantages like reduced attenuation and scintillation effects in certain atmospheric conditions along with very high level of data security. In this work, we propose a scheme to realize Quantum Memory (QM) for efficient storage of terahertz (THz) frequency signals using Electromagnetically Induced Transparency (EIT) in an ultracold atomic medium of 87Rb Rydberg atoms prepared in a Two Dimensional Magneto Optical Trap (2D-MOT). The uniqueness of our scheme lies in the choice of the energy levels involved in the EIT process, all three of which have been chosen to be the Rydberg levels (enabling signal beam to be in THz) in a lambda type arrangement. This first of its kind proposal reveals that atomic media are a potential candidate for devising QMs which can store THz frequency signals. We have estimated that the Optical Depth (OD) in our scheme can reach a very high value of 690, very high maximum obtainable storage efficiency (η) of ∼99%, the group velocity ( v g ) can be as low as 5.07 × 103 m/s, and the Delay Bandwidth Product (DBP) can be as high as 9.5. All of these estimates emphasize the feasibility of our scheme as a QM device for efficient storage of THz pulses.

We report calculations of accurate high lying resonance energies of the [ 3 s 3 2 p ( D 5 / 2 ° 2 ) 3 ]nd and [ 3 s 3 2 p ( P 3 / 2 ° 2 ) 3 ]nd Rydberg series originating from the ground 3 s 3 2 p 4 P 2 3 and from the 3 s 3 2 p 4 P 1 , 0 3 metastable states of Cl+ along with the [ 3 s 3 2 p ( P 1 / 2 ° 2 ) 3 ]nd Rydberg series originating from the 3 s 3 2 p 4 S 0 1 metastable state of the Cl+ ion. Calculations are performed using the Screening Constant by Unit Nuclear Charge (SCUNC) method up to n = 40. The results obtained are compared with the existing Dirac – Coulomb R-matrix (DCR) calculations (McLaughlin, 2017) and Advanced Light Source (ALS) measurements (Hernandez et al., 2015). Analysis of the present results is achieved in the framework of the standard quantum-defect theory and of the SCUNC-procedure based on the calculation of the effective charge. It is shown that the SCUNC-method agree very well the ALS measurements up to n = 13. New high lying accurate resonance energies (n = 14–40) are tabulated as benchmarked data for the atomic physics community in connection with the modeling of plasma and astrophysical systems.

The photodissociation dynamics of methyl radical from selected vibrational levels of the 3 s and 3 p z Rydberg states has been studied using the trajectory surface hopping method on one-dimensional potential energy curves along the carbon-hydrogen dissociative coordinate and the non-adiabatic couplings between them, calculated by ab initio methods. Lifetimes and product distributions have been obtained for all the studied vibrational levels and compared with previous theoretical and experimental works. The theoretical lifetimes tend to decrease as vibrational excitation increases in accordance with experimental results. The agreement, however, is only qualitative considering the reduced dimensionality of the model.

An finite-nuclear-mass (FNM) approach is employed to describe the magnetic orbit-orbit interaction of the electrons and the nucleus orbiting around the center of mass of the helium atom in 1S and 1P Rydberg states. The calculations are performed using explicitly correlated Gaussian functions to expand the states’ wave functions. The non-linear parameters of the Gaussians are optimized using a variational approach employing the analytical energy gradient. An FNM and INM (infinite-nuclear-mass) approaches are used in the optimization and compared.

Dielectronic recombination (DR) and radiative recombination (RR) spectra of highly charged Tungsten ions are important for modeling and diagnosing magnetic fusion plasmas. We studied the DR process of Li-like W 71 + (2s) ions using the flexible atomic code (FAC) based on the relativistic configuration interaction (RCI) method with Breit and QED corrections. The detailed resonance energies, widths and strengths were calculated systematically for the dominated doubly excited states ( 2 p 1 / 2 n l j ) J ( n = 19 ∼ 29 ) and ( 2 p 3 / 2 n ′ l j ) J ( n ′ = 7 ∼ 29 ) of Be-like W 70 + ions. The contributions from the higher Rydberg states with n = 30 ∼ n c u t ( n c u t = 116 ) are obtained by extrapolation based on the quantum defect theory (QDT). The electron-ion recombination spectra (DR+RR), covering the center-of-mass energy range 0–1700 eV, are presented by taking into account the electron beam temperature at the experimental cooler storage ring (CSRe). It is found that the DR resonances associated with 2s1/2 → 2p1/2 and 2s1/2 → 2p3/2 transitions are not blending for the whole Δ n = 0 collision energy range, which will provide a good chance for testing fundamental theory clearly by experimental investigation. Finally the plasma rate coefficients are deduced from the calculated recombination spectra in the temperature range from 5.0 × 103 to 1.0 × 108 K. Compared with the AUTOSTUCTURE results, a good agreement is obtained except for the DR rates at the low electron temperature (Te

An ellipsoidal volume of Rydberg molecules, entrained in a supersonic molecular beam, evolves on a nanosecond timescale to form a strongly coupled ultracold plasma. We present coupled rate-equation simulations that model the underlying kinetic processes and molecular dissociation channels in both a uniformly distributed plasma and under the conditions dictated by our experimental geometry. Simulations predict a fast electron-driven collisional avalanche to plasma followed by slow electron-ion recombination. Within 20 μs, release of Rydberg binding energy raises the electron temperature of a static plasma to T e = 100 K. Providing for a quasi-self-similar expansion, the hot electron gas drives ion radial motion, reducing T e . These simulations provide a classical baseline model from which to consider quantum effects in the evolution of charge gradients and ambipolar forces in an experimental system undergoing responsive avalanche dynamics.

VUV photoabsorption spectrum of dimethyl carbonate in the energy region 7–11 eV and its complete spectral analysis with the aid of quantum chemical calculations is reported for the first time. The spectrum recorded using synchrotron radiation comprises of weak bands overlapping a broad intense continuum. With a view to interpret possible vibronic structure, gas phase infrared spectrum in the region 500–4000 cm−1 is revisited. Density functional theory (DFT) and time dependent DFT (TDDFT) methodologies are used to obtain ground state geometry, vibrational frequencies and vertical excitation energies of dimethyl carbonate. The intense broad features in the spectrum could be attributed to valence transitions. Based on quantum defect calculations, energy ordering and symmetry, weak bands are designated as ns, np and nd type Rydberg transitions converging to the first five ionization potentials. The highest occupied molecular orbital is nonbonding in nature and largely localized on the oxygen atom of carbonyl group and quantum defect values obtained are consistent with excitation from oxygen lone pair. Excellent correlation is obtained between theoretically predicted (CAM-B3LYP levels of theory) and experimentally observed excited state energies. Potential energy curves of ground and first few excited states generated with a view to provide additional insights into their nature and further describe the observed spectra. The present study provides a comprehensive experimental and computation analysis of the VUV photoabsorption spectroscopy of dimethyl carbonate.

The electronic spectra of diethyl carbonate (DEC) based on photoabsorption spectroscopy using synchrotron radiation are investigated in the 6.8-11.5 eV region. The VUV photo absorption spectrum reported here for the first time comprises broad features in the 7-11 eV region with few weak overriding spectral peaks. The broad peaks could be assigned to valence excitations, while the weak ones correspond to the Rydberg series of ns, np, and nd types, thus converging to the first five ionization potentials. Quantum defect values obtained are consistent with the excitation of an electron from oxygen lone pair. Infrared bands of DEC were revisited in the 600-3100 cm−1 region. The observed infrared bands of DEC could be assigned by DFT calculations. The TDDFT methodology is used to compute the vertical excited state energies, valence/Rydberg nature, and oscillator strengths of the excited electronic states. A good agreement using the CAM-B3LYP level of theory is achieved between the theoretically predicted values and experimental observations. In the ionic limit of DEC, the lengthening of the C O and CO–C2H5 bond lengths is predicted. The potential energy curves of the first few excited states assisted in additional insights on the nature of the excited states and their role in photo dissociation dynamics. This study gives a first comprehensive report on the analysis of absorption spectra of DEC in the VUV region and the complete spectral assignments in the VUV and IR regions by quantum chemical calculations.

We report term energies and effective quantum numbers of the odd-parity 4snf 1F3 Rydberg series of zinc from 75,480 to 75,750 cm−1 energy range. The experiment was performed using three dye lasers simultaneously pumped by the second (532 nm) and third (355 nm) harmonics of a Q-switched Nd-YAG laser in conjunction with an atomic beam set-up. The new observation include the 4snf 1F3 (20 ≤ n ≤ 50) series excited from the 4s4d 1D2 intermediate level. In addition, the dipole polarizability of the zinc core is determined as αd = 18.33 ± 0.95 ao3 using the core polarization model, which is in consistence with the earlier reported experimental and theoretical results.

We propose a scheme to investigate vector spatio-temporal soliton pairs via double Rydberg electromagnetically induced transparency (EIT). We show that three dimensional (3D) vector monopole and vortex solitons, with ultralow generation power and ultraslow speed, have been found under three response regions. In particular, these spatio-temporal soliton pairs experience a significant Stern-Gerlach deflection when a gradient magnetic field is applied to the system. The results reported here are useful not only for extending the research realm of nonlinear magneto-optics but also for the application in the detection of microgradient magnetic fields.

A comprehensive spectroscopic study of the UV–VUV photoabsorption spectrum of nitromethane in the energy region 5.4–11.8 eV (43,500–95,000 cm−1) using synchrotron radiation is presented; the VUV absorption spectrum in the region > 9 eV being reported for the first time. The observed spectral features are assigned to various valence and Rydberg transitions, supported by quantum chemical calculations using the TDDFT method. The 6 eV region is dominated by a broad, intense absorption band peaking at ∼ 6.2 eV assigned to the π-π* valence transition, followed by rich Rydberg series converging to the first four ionization potentials of nitromethane. Theoretical calculations of orbital energies as well as Rydberg series analysis indicate that the third IP is located at 11.95 eV, in contrast to the earlier estimated value of 11.5 eV. Series of bands attributed to vibrational transitions accompanying the 3s (6a″), 3p(6a"), 3s(10a′) and 3s(5a″) Rydberg transitions are observed in the 60,000–73,000 cm−1 region and are tentatively assigned to progressions involving the NO2 in-plane rock and CH3 asymmetric deform modes. The liquid phase IR spectrum is revisited and assigned with the help of DFT calculations. A few new bands are observed and assigned to overtone and combination modes. Theoretically simulated potential energy curves of the first few excited singlet and triplet states with respect to the CN and NO bond lengths are useful in explaining some of the incompletely understood features of the photodissociation dynamics of nitromethane. It is found that direct dissociation in the Franck Condon region is a possible mechanism for the CH3NO + O channel, while singlet-triplet crossings play an important role in CN and NO bond scissions.

Vacuum ultraviolet photoabsorption spectra of pentane (C5H12) structural isomers (n-pentane and isopentane) are recorded in the 6–11.5 eV region using a synchrotron light source. The photoabsorption spectra for both the pentane isomers showed a continuum, beginning at about 7.5 eV and increasing in intensity up to 10.5 eV with few broad peaks devoid of discernible structures. Quantum chemical calculations using the DFT methodology predicted the optimized ground geometry and fundamental frequencies for neutral and cationic pentane isomers. The excited electronic state vertical energies are computed using time-dependent DFT and allied to construe the experimental spectra. From theory, the electronic spectra of pentane isomers encompass mostly valence-Rydberg mixed type transitions, converging to the first four ionization potentials while isopentane at 9.62 eV predicted a uni-molecular dissociation to C2H5• and C3H7• radicals. The plot of potential energy curves for the first few excited states facilitated understanding the spectral features UV region and its photodissociation mechanism for both pentanes. The broad continuum spectra in both isomers may be attributed to strong valence - Rydberg interactions along with a contribution from the presence of conformers, low torsional modes and Rydberg series converging to close-lying ionization potentials. Gas phase infrared spectra of pentane isomers in the 500–4000 cm−1 region were revisited and DFT calculations clarified few vibrational assignments. The present study provides a comprehensive understanding of the absorption spectra in the VUV and IR regions of n-pentane and isopentane.

Vertical excitation energies belonging to several Rydberg series of MgH have been inferred from 3+ electron-propagator calculations of the electron affinities of MgH+ and are in close agreement with experiment. Many electronically excited states with n > 3 are reported for the first time and new insight is given on the assignment of several Rydberg series. Valence and Rydberg excited states of MgH are distinguished respectively by high and low pole strengths corresponding to Dyson orbitals of electron attachment to the cation. By applying the Molecular Quantum Defect Orbital method, oscillator strengths for electronic transitions involving Rydberg states also have been determined.

A theoretical investigation of the atomic structure and radiative parameters involving the lowest states within the 6p5, 6p47s and 6p47p configurations of neutral astatine is reported for the first time in the present paper. Using different physical models based on the pseudo-relativistic Hartree–Fock approach, the influence of intravalence, core-valence and core-core electron correlation on the atomic parameters is discussed in detail. This work allowed us to establish the intermediate-coupling composition and to clearly fix the spectroscopic designation of six excited levels within the 6p47s and 6p47p configurations which had been located in previous experimental studies. In addition new tentative identifications of four levels belonging to the 6p49p and 6p410p configurations are reported in this work together with predicted level energies along the 6p4np and 6p4nd Rydberg series up to n = 50.

We report Photoionization calculations on the Ne-like ( Z = 27-56) ions for resonance energies of the 1s 2 2s2p 6 n p 1 P series. The calculations are performed in the framework of the Screening constant by unit nuclear charge (SCUNC) method. Good agreements are found with available literature data for the Ne-like Cu 19+ , Kr 26+ and Xe 34+ ions. New data for the Ne-like ( Z = 27, 28, 30–35, 37–43, 45–56) ions are tabulated as useful guidelines for modelling astrophysical and laboratory plasmas.

The predissociation-mediated excited state decays for several vibronic levels of the B and C Rydberg states of axial-iodocyclohexane (axial-c-C6H11I) are investigated with time-resolved mass spectrometry. The B or C state of axial-c-C6H11I was selectively excited with tunable VUV femtosecond laser at wavelengths of 204.2 nm-201.5 nm. The following predissociation decay via the crossing between the Rydberg states and the repulsive A-band was observed and the lifetimes were measured to be

A cold atomic gases system with parity-time (PT) symmetry is proposed to generate stable solitons. The Rydberg atomic gases and electromagnetically induced transparency are utilized in the interaction between the transmission of signals and atomic lattices. Two kinds of two-dimensional (2D) multipole solitons (MSs), two pole and four pole solitons, are found in this cold atomic system. We investigate the existence conditions and the stability of these solitons. The results show that these solitons can stably propagate in this system, and can be manipulated by the system parameters of nonlocal nonlinearity and PT potential.

We report the measurement of the quantum defects of 85Rb P3/2 and F7/2-series Rydberg levels in a room temperature vapor cell by microwave-assisted electromagnetically induced transparency (EIT) spectroscopy. First, a novel microwave optical three-photon excitation method is employed to obtain the microwave-assisted EIT spectroscopy of the 5S1/2 − 5P3/2 – nD5/2 – (n+1)P3/2 or (n-1)F7/2 transition. Next, the Stark shifts of the corresponding Rydberg states relative to the Rabi frequency of microwave field are measured with high accuracy. Finally, the quantum defects, δ0 = 2.64142(15), δ2 = 0.295 for P3/2-series, and δ0 = 0.016411(16), δ2 = -0.0784 for F7/2-series, are forcibly extracted by the modified Rydberg-Ritz formula. This result can serve as a check on advanced theoretical calculations and promote the application of quantum simulations and quantum sensors in atomic ensembles.

A detailed spectroscopic study on ethyl methyl carbonate, a green solvent, has been carried out by recording vacuum ultraviolet and infrared spectra. The vacuum ultraviolet photoabsorption spectrum is recorded using synchrotron radiation from Photophysics beamline at the Indus-1 synchrotron radiation source at RRCAT, Indore, India in the wavelength region of 7–11.5 eV. Infrared spectra in gas phase as well as matrix isolated case are recorded using an indigenously developed laboratory low temperature experimental facility and a Fourier transform infrared spectrometer in the 500–4000 cm−1 region. Geometry optimization, vibrational frequency analysis of neutral & ionized ethyl methyl carbonate and electronic excited state energy information has been obtained using quantum chemical calculations. The observed ir spectral features could be assigned to the fundamental vibrational modes of the molecule. The vacuum ultraviolet region comprising a broad continuum is assigned to valence transitions having high oscillator strengths and overlying weak bands to ns, np, nd type Rydberg transitions. Potential energy curves of the ground and first few low lying excited states generated provided additional insights into their nature and further interpretation of observed experimental spectra. In this paper we report the first electronic absorption spectrum in 7 to 11.5 eV region, its spectroscopic analysis and identification of vibrational modes in the infrared spectra for ethyl methyl carbonate. Results of quantum chemical simulations carried out to obtain nature of excited states, energies and vibrational frequencies using GAMESS (USA) quantum chemistry code are also reported in this paper.

Hydrogen fluoride (HF) has served as a benchmark molecule for ab initio methods. Consequently, it has been extensively investigated in the past few decades. The energy ordering of the low-lying triplet electronic states has proven controversial in previous computational studies. In this work, the Gaussian basis of F and H atoms are calibrated by adding diffuse functions to the aug-cc-pV5Z valence basis sets. The electronic structure of HF molecule is studied by the multireference configuration interaction method plus Davidson correction method (MRCI+Q). The potential energy curves (PECs) of 19 electronic states are computed, and the spectroscopic constants of the bound states are determined. The low-lying triplet Rydberg electronic states 23Σ+ (3Σ+R1), 23Π (3ΠR1) and 13Δ (3ΔR1) are characterized and compared with the previous computational results. The transition dipole moments (TDMs) and Franck-Condon factors (FCFs) between the electronic states are subsequently calculated. Finally, the spontaneous radiative lifetimes of four spin-allowed transitions are obtained. The results of this paper will improve the understanding on the electronic excited states of HF molecule, especially the electronic structure and spectra characteristics of the triplet excited states.

The screening induced by a dense plasma environment is crucially important for determining radiative atomic data including bound–bound radiative decay rates and photoionization cross sections, which are vital for obtaining accurate opacity. Previous experimental investigations of ionization potential depression have shown that the widely used analytical models of screening struggle to capture the essential physics in the solid-density plasma. In the present work, we investigate how plasma screening affects the radiative atomic data of Si 10 + –Si 13 + embedded in a dense plasma environment using a self-consistent field finite temperature ion sphere model. The single-electron effective potential of an embedded atom has a short-range feature that determines the available number of bound states. Plasma screening is effective in modifying the matrix elements of the radiative dipole transitions, thereby generally increasing the photoionization cross section near the ionization threshold and decreasing the bound–bound radiative decay rates. The enhancement of the photoionization processes stems from lowering the ionization threshold and the shape and virtual-state resonances, where the upper bound levels become delocalized after a certain critical screening strength. With increasing plasma density, the Rydberg series for the bound–bound radiative transitions disappear successively.

International audience; VUV photoionization dynamics of the S2 molecule were re-investigated from threshold up to 15.0 eV, using synchrotron radiation coupled with double imaging photoelectron/photoion coincidence featuring high resolution capabilities. We measured the first threshold photoelectron spectrum of S2 achieving higher resolution than previous literature to derive accurate spectroscopic constants for a few electronic states of the cation including the X 2 PW, g ground state and the a 4 Pu, b 4 Sg-, and B 2 Sgstates. We also recorded the total ion yield for S2 up to a photon energy of 15.0 eV which, combined with the threshold photoelectron spectrum, led to the assignment of various autoionizing Rydberg series.

High-accuracy calculations are performed on the 1 D spectrum of beryllium with the use of all-electron explicitly correlated Gaussian (ECG) functions. In the first step, a nonrelativistic wave function is generated for each state with the ECG nonlinear parameters variationally optimized using a procedure employing energy gradient determined with respect to these parameters. The wave functions are used to calculate the leading relativistic corrections employing the recently implemented algorithms. The state total energies and the interstate transition energies are compared with the high-quality experimental results.

We report the first observation of photoluminescence from excitonic Rydberg states with quantum number n up to 7 in Cu2O. We find that the luminescence linewidths increase at elevated temperatures and under increased laser power, and that the effect is more pronounced for a state with a larger n. The temperature dependence is attributed to scattering by longitudinal-optical phonons, whereas the density dependence is explained by the binary collisions of excitons in the ground ( n = 1 ) and excited ( n ≥ 2 ) Rydberg states. The n-dependent broadening is discussed on the basis of the overlap of wave functions and collision cross sections determined by the Bohr radius of Rydberg excitons.

Mass resolved resonance enhanced multiphoton ionization (REMPI) spectra of a mixture of DCl and HCl were recorded for two-photon resonance excitation in the region of 80 500–89 500 cm−1. Spectra due to resonance transitions to rovibrational states of number of Rydberg and ion-pair states of DCl, were identified and assigned. Five new spectral bands due to transitions to Rydberg states and eight new bands due to transitions to vibrational states of the ion-pair state were identified and analysed to derive energetic parameters. Irregularities observed in vibrational energy level spacing, rotational constants and isotope shifts of chlorine isotopologues from what to expect for unperturbed states, as well as relative signal intensities, are indicative of strong homogeneous interaction between the E1Σ+ Rydberg state and the V1Σ+ ion-pair state. These observations are found to be due to level-to-level interaction between E and V rovibrational states of same J′ quantum numbers. Comparison of the data for DCl and HCl is performed.

Present nuclear detection techniques prevents us from determining if the analogue of a Rydberg molecule exists for the nuclear case. But nothing in nature disallows their existence. As in the atomic case, Rydberg nuclear molecules would be a laboratory for new aspects and applications of nuclear physics. We propose that Rydberg nuclear molecules, which represent the exotic, halo nuclei version, such as 11Be + 11Be, of the well known quasimolecules observed in stable nuclei such as 12C + 12C, might be common structures that could manifest their existence along the dripline. A study of possible candidates and the expected structure of such exotic clustering of two halo nuclei: the Rydberg nuclear molecules, is made on the basis of three diferent methods. It is shown that such cluster structures might be stable and unexpectedly common., 6 pages, 4 figures, revised text, accepted for publication in Physics Letters B

We performed spectroscopic measurements of the 3 snp (21 ≤ n ≤ 51) 3 P° and the 3 snf (26 ≤ n ≤ 55) 3 F° Rydberg states of magnesium (Mg) atom using two-step laser resonant excitation of Mg in the 3 s 3 p 3 P° metastable states. The metastable states of Mg were produced in a pulsed discharge, which was initiated each time a Mg rod was ablated by a pulsed Nd:YAG laser in between low-voltage electrodes. The quantum defects of the 3 snp 3 P 0 , 1 ∘ and the 3 snf 3 F 2 , 3 ∘ states were determined as 1.114(6) and 0.04(1), respectively.

Eight doubly excited 1 , 3 P ° resonances in He-like systems below the N = 3 hydrogenic threshold are investigated in the framework of Screening Constant by Unit Nuclear Charge (SCUNC) formalism. The Rydberg series investigated are labelled in the ( K , T , A ) classification scheme. Accurate data are tabulated for the entire He-isoelectronic sequence up to Z = 40 with 3 ≤ n ≤ 9 , n the principal quantum number of the outer electron.

Nuclear and electronic dynamics in a wavepacket comprising bound Rydberg and valence electronic states of nitrogen from 12 to 15 eV are investigated using attosecond transient absorption. Vibrational quantum beats with a fundamental period of 50 femtoseconds persist for a picosecond in the b′ 1Σ+u valence state. Multi-state calculations show that these coherences result primarily from near infrared-induced coupling between the inner and outer regions of the b′ 1Σ+u state potential and the dark a″ 1Σ+g state. The excellent spectral and temporal resolution of this technique allows measurement of the anharmonicity of the b′ 1Σ+u potential directly from the observed quantum beats.

Over a thousand spectral lines in the photoexcitation spectrum of molecular deuterium (D2) to np 1 Σ u + and 1 Π u + Rydberg levels ( n ⩾ 4 ) were measured for rotational levels N ′ = 1 –6 in the 117 000–137 000 cm−1 spectral range by two different types of experiments at two synchrotron radiation sources: a vacuum ultraviolet (VUV) Fourier-transform (FT) spectrometer at SOLEIL, Paris and a 10 m-normal-incidence monochromator (NIM) at BESSY II, Berlin. The experimental energies, the absorption cross sections, Einstein A-coefficients, and line widths are compared with ab initio multi-channel quantum defect (MQDT) calculations for these levels. More than 350 R(0) or P(2) lines were assigned, some 280 R(1) or P(3) lines, some 270 R(2) or P(4) lines, over 100 R(3) or P(5) lines, over 90 R(4) lines, and 24 R(5) lines to extract information on the N ′ = 1 –6 excited levels. Transition energies were determined up to excitation energies of 137 000 cm−1 above the ground state, thereby extending earlier work by various authors and considerably improving the spectral accuracy ( 0.1 cm−1), leading to several reassignments. The absorption and the dissociation, ionization and fluorescence excitation cross sections from the NIM experiment are measured on absolute scale and are used to calibrate intensities in the VUV-FT spectra. The overall agreement between experiment and first principles calculations, without adjustable parameters, is excellent in view of the multi-state interferences treated within the MQDT-framework: For the low N ′ values the averaged deviations between those observed in the FT-SOLEIL spectra and those calculated with MQDT are ∼ 0.1 cm−1 with a spread of ∼ 0.5 cm−1. The line intensities in terms of Einstein coefficients are well represented in the MQDT-framework, as are the level widths representing the lifetimes associated with the sum of the three decay channels. These line intensities follow, in general, the 1 / n 3 scaling behavior as characteristic in Rydberg series, but deviations occur and those are explained by MQDT. The decay dynamics of the excited N Rydberg levels is analyzed on the basis of the measured quantum yields for ionization, dissociation and fluorescence observed in the NIM experiment in terms of absolute cross sections for the distinctive channels. In particular in the n = 4 manifolds dissociation is found to play a major role, where in the n = 5 manifolds the behavior is most erratic due to strong competition between decay channels. At n = 6 , ionization takes over as the dominant channel. Despite the excellent agreement between observations and the outcome of the MQDT calculations for both level energies and dynamics, some pronounced deviations are found as in the splitting of the 5 p π , v = 4 –6, N ′ = 1 levels. The shortcomings of the MQDT calculations are ascribed to the treatment of the excited states in terms of a 1 snp single electron configuration, therewith neglecting possible interferences with 1 snf or 2 s core excited states. Some 27 lines remained unassigned; in view of their observation in fluorescence it is stipulated that these lines probe levels in the nf manifold.

Highly correlated ab initio calculations were performed in order to obtain an accurate determination of the γ (A 2 Σ + -X 2 П) system and β (B 2 П-X 2 П) system of the NO molecule. The multi-reference configuration interaction (MRCI) approach was used to investigate the potential energy curves and transition dipole moment curves of the γ and β systems. The potential energy curves of the three states agreed well with Rydberg-Klein-Rees (RKR) potential using aug-cc-pV5Z basis set. The active space had a significant influence on transition dipole moment curves, but it hardly effected on potential energy curves. We find that using a (4s/4πx/4πy/0δ) active space produces results significantly closer to experiment than a (4s/3πx/3πy/0δ) active space. We correctly and fully described their diffuse wave functions by the obvious balance between valence and Rydberg character of X 2 П, A 2 Σ + , and B 2 П states. Moreover, the Einstein A coefficient were calculated to predict the absolute intensities. The line lists were presented the intensities of γ system and β system from 296 K to 6000 K which included 0-0, 0-1, 0-2, 0-3, 1-0, 1-1, 1-2, and 2-0 bands.

We present a theoretical scenario for the atomic above-threshold ionization (ATI) in an intense laser field by investigating the Rydberg state population in real time. Rather than merely viewing the final distribution of photoelectron yield directly, we monitor the Rydberg state population by projecting the time-dependent wave function onto the bound eigen-states. The calculation shows that the population of resonant Rydberg states is closely related to the peaks in photoelectron kinetic energy spectrum (PKES). For a hydrogen atom, the highest populated Rydberg states are degenerated, exactly corresponding to the first ATI peak if one additional photon is absorbed. While for non-hydrogen atoms, e.g., Ar, the highest Rydberg states are mainly populated on specific states, e.g., 3 d ( 5 s ) and 4f in our case, also giving exact peak positions in PKES, where the state identification is obtained by the angular momentum resolved distribution of excited Rydberg states. This method provides an easy to understand picture for the resonance-enhanced effects in ATI as well as the role of atomic core potential in strong-field ionization.