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The microwave spectra of benzothiazole were measured in the frequency range 2–26.5 GHz using a pulsed molecular jet Fourier transform microwave spectrometer. Hyperfine splittings arising from the quadrupole coupling of the 14N nucleus were fully resolved and analyzed simultaneously with the rotational frequencies. In total, 194 and 92 hyperfine components of the main species and the 34S isotopologue, respectively, were measured and fitted to measurement accuracy using a semi-rigid rotor model supplemented by a Hamiltonian accounting for the 14N nuclear quadrupole coupling effect. Highly accurate rotational constants, centrifugal distortion constants, and 14N nuclear quadrupole coupling constants were deduced. A large number of method and basis set combinations were used to optimize the molecular geometry of benzothiazole, and the calculated rotational constants were compared with the experimentally determined constants in the course of a benchmarking effort. The similar value of the χcc quadrupole coupling constant when compared to other thiazole derivatives indicates only very small changes of the electronic environment at the nitrogen nucleus in these compounds. The small negative inertial defect of −0.056 uÅ2 hints that low-frequency out-of-plane vibrations are present in benzothiazole, similar to the observation for some other planar aromatic molecules. [ABSTRACT FROM AUTHOR]

The influence of magnetic fields on chemical reactions, including biological ones, has been and still is a topical subject in the field of scientific research. Experimentally discovered and theoretically substantiated magnetic and spin effects in chemical radical reactions form the basis of research in the field of spin chemistry. In the present work, the effect of a magnetic field on the rate constant of the bimolecular spin-selective recombination of radicals in the bulk of a solution is considered theoretically for the first time, taking into account the hyperfine interaction of radical spins with their magnetic nuclei. In addition, the paramagnetic relaxation of unpaired spins of the radicals and the non-equality of their g-factors that also influence the recombination process are taken into account. It is found that the reaction rate constant can vary in magnetic field from a few to half a dozen percent, depending on the relative diffusion coefficient of radicals, which is determined by the solution viscosity. It is shown that the consideration of hyperfine interactions gives rise to the presence of resonances in the dependence of the rate constant on the magnetic field. The magnitudes of the magnetic fields of these resonances are determined by the hyperfine coupling constants and difference in the g-factors of the recombining radicals. Analytical expressions for the reaction rate constant of the bulk recombination for magnetic fields larger than hfi (hyperfine interaction) constants are obtained. In general, it is shown for the first time that accounting for hyperfine interactions of radical spins with magnetic nuclei significantly affects the dependence of the reaction rate constant of the bulk radical recombination on the magnetic field. [ABSTRACT FROM AUTHOR]

The Overhauser Dynamic Nuclear Polarization (O‐DNP) of 1H nuclei usually involves a dipolar coupling with the polarizing agent, whereas scalar coupling via hyperfine interactions are more common with 13C nuclei. Here, we show a scalar‐coupling dominated 1H O‐DNP, using polyaniline as a heterogeneous polarizing agent in an aqueous solution. [ABSTRACT FROM AUTHOR]

Identification of the external electromagnetic fields and internal hyperfine parameters which optimize the quantum singlet-triplet yield of simplified radical pairs modeled by Schrödinger system with spin Hamiltonians given by the sum of Zeeman interaction and hyperfine coupling interaction terms are analyzed. A method that combines sensitivity analysis with Tikhonov regularization is implemented. Numerical results demonstrate that the quantum singlet-triplet yield of the radical pair system can be significantly reduced if optimization is pursued simultaneously for both external magnetic fields and internal hyperfine parameters. The results may contribute towards understanding the structure-function relationship of a putative magnetoreceptor to manipulate and enhance quantum coherences at room temperature and leveraging biofidelic function to inspire novel quantum devices. [ABSTRACT FROM AUTHOR]

A test set of N,N,N',N'-tetrasubstituted p-phenylenediamines are experimentally explored using ESR (electron spin resonance) spectroscopy and analysed from a computational standpoint thereafter. This computational study aims to further aid structural characterisation by comparing experimental ESR hyperfine coupling constants (hfccs) with computed values calculated using ESR-optimised "J-style" basis sets (6-31G(d,p)-J, 6-31G(d,p)-J, 6-311++G(d,p)-J, pcJ-1, pcJ-2 and cc-pVTZ-J) and hybrid-DFT functionals (B3LYP, PBE0, TPSSh, ω B97XD) as well as MP2. PBE0/6-31g(d,p)-J with a polarised continuum solvation model (PCM) correlated best with the experiment, giving an R 2 value of 0.8926. A total of 98% of couplings were deemed satisfactory, with five couplings observed as outlier results, thus degrading correlation values significantly. A higher-level electronic structure method, namely MP2, was sought to improve outlier couplings, but only a minority of couples showed improvement, whilst the remaining majority of couplings were negatively degraded. [ABSTRACT FROM AUTHOR]

M-type Barium hexaferrite is a famous hard magnetic material with a hexagonal crystal structure. La substituted Barium hexaferrite, Ba(1-x)La(x)Fe12O19, (where, x = 0.25 and 0.30) were synthesized using ball milling followed by sintering at 1300 °C for 5 hours. X-ray diffraction patterns reveal the formation of a single-phase magnetoplumbite structure of barium hexaferrite, which belongs to the P63/mmc space group. Mossbauer spectroscopic studies were carried out to study the magnetic phase, the effect of La doping on the valency of the Fe atom, and charge distribution in the prepared samples. Mossbauer spectra is fitted using 5 sextets, shows there is 5 sublattices present in the system. From the fitting of Mossbauer spectrum, it is observed that, there is no formation of Fe2+ ion even if the doping levels are as high as 30%, as it is expected that Fe3+ ion changes its valance to maintain the charge neutrality. However, there is an increase in s-electron density for number of sites with doping. Quadrupole splitting values shows spherical charge distribution for all the sublattices except 2b, due to asymmetric nature of bipyramidal site. Slightly varied magnetic hyperfine splitting values are observed for 12 k and 4f1 sites shows the effect of La substitution. [ABSTRACT FROM AUTHOR]

Photoexcited organic chromophores appended to stable radicals can serve as qubit and/or qudit candidates for quantum information applications. 1,6,7,12‐Tetra‐(4‐tert‐butylphenoxy)‐perylene‐3,4 : 9,10‐bis(dicarboximide) (tpPDI) linked to a partially deuterated α,γ‐bisdiphenylene‐β‐phenylallyl radical (BDPA‐d16) was synthesized and characterized by time‐resolved optical and electron paramagnetic resonance (EPR) spectroscopies. Photoexcitation of tpPDI‐BDPA‐d16 results in ultrafast radical‐enhanced intersystem crossing to produce a quartet state (Q) followed by formation of a spin‐polarized doublet ground state (D0). Pulse‐EPR experiments confirmed the spin multiplicity of Q and yielded coherence times of Tm=2.1±0.1 μs and 2.8±0.2 μs for Q and D0, respectively. BDPA‐d16 eliminates the dominant 1H hyperfine couplings, resulting in a single narrow line for both the Q and D0 states, which enhances the spectral resolution needed for good qubit addressability. [ABSTRACT FROM AUTHOR]

SrF, being a laser-coolable molecule, can be an interesting system for spectroscopic tests of fundamental physics. We present an electronic structure study of this molecule within the four-component relativistic coupled-cluster singles and doubles (RCCSD) framework and employ the RCCSD-based methods to compute its molecular-frame dipole moment and core properties such as hyperfine structure coupling constant and molecular P, T-odd electronic structure parameters that are of great importance for the high-precision tests of fundamental physics. The impact of basis set size, Hamiltonian and nuclear model on the property calculation of SrF is also investigated. The computed results are in good agreement with the available experimental values. The present study shows that the SrF molecule could be useful for high-precision molecular experiments to explore physics beyond the Standard Model of elementary particles. [ABSTRACT FROM AUTHOR]

We have prepared trityl radicals with protons at the positions of the -COOH group in the phenyl rings and examined their EPR spectra, which show large ▪ - ▪ hyperfine couplings, and their dynamic nuclear polarization (DNP) Zeeman field profiles. By assessing these polarizing agents for high-field and Overhauser effect DNP, we gain insight into the roles that these hyperfine couplings and other molecular properties play in the DNP performance of these radicals. Interestingly, we do not observe OE DNP in any of the three molecules we examined. This suggests that hyperfine couplings by themselves are not sufficient to support OE DNP. In this case the electron spin density is ∼ 75 % localized on the central carbon atom rather than being distributed uniformly over the aromatic rings. This is in contrast to BDPA where the distribution is delocalized. Our findings do not suggest that any of these radicals are particularly well-suited to high-field DNP. Furthermore, we emphasize that polarizing agents can be extremely sensitive to their solvent environment, even obscuring the intrinsic magnetic properties of the radical. [Display omitted] • A series of modified trityl radicals were studied to examine the effect of large isotropic hyperfine couplings on an otherwise narrow-line radical. • The couplings were found not to be sufficient for an Overhauser-like enhancement profile. • The absence of an Overhauser effect is in contrast to what is observed in BDPA. • Electron delocalization in trityl may be responsible for the absence of an Overhauser effect. [ABSTRACT FROM AUTHOR]

The 1S hyperfine splitting in hydrogen is measured to an impressive ppt precision and will soon be measured to ppm precision in muonic hydrogen. The latter measurement will rely on theoretical predictions, which are limited by knowledge of the proton polarizability effect Δ pol. Data-driven evaluations of Δ pol have long been in significant tension with baryon chiral perturbation theory. Here we present improved results for Δ pol driven by new spin structure data, reducing the long-standing tension between theory and experiment and halving the dominating uncertainty in hyperfine splitting calculations. [ABSTRACT FROM AUTHOR]

A pulsed, tunable, narrow linewidth mid-infrared (mid-IR) laser radiation source was developed to meet the needs of the FAMU project (Fisica Atomi MUonici). The main goal of this experiment is to measure the hyperfine splitting of the ground state of muonic hydrogen using pulsed laser spectroscopy. The experiment requires a high energy, mid-IR source around the resonance energy Δ E1S h f s ∼ 0.1828 eV (6. 79 μ m) of the muonic hydrogen atom to excite it from the para (F = 0) to the ortho (F = 1) spin state. The laser system designed to fulfill these requirements is based on Difference Frequency Generation (DFG) using a non-linear crystal pumped by two laser beams at 1064 nm and 1262 nm. For the first time, the details of the entire laser system are described in this paper. The laser light at 6. 79 μ m , generated with a BaGa 4 Se 7 non-linear crystal, is being directed into the FAMU target multi-pass optical cavity. To date, an energy above 1 mJ, a linewidth below 30 pm, and a tunability step of 9 pm have all been attained. Here, we present the unique features of the laser system and the characterization results. • As the core of a crucial spectroscopy experiment on muonic hydrogen the FAMU laser has complied with the basic specifications and will be used during the next data taking. • This mid-IR laser source is based on nonlinear optics using a BaGa 4 Se 7 crystal and DFG process. • The FAMU mid-IR laser is tuneable and produces a narrow linewidth beam between 6730 and 7135 nm. • The energy produced by the FAMU laser exceeds 1,1 mJ at 6,79 nm and linewidth below 30 pm. [ABSTRACT FROM AUTHOR]

We present a Rabi-type measurement of two ground-state hydrogen hyperfine transitions performed in two opposite external magnetic field directions. This puts first constraints at the level of ▪ on a set of coefficients of the Standard Model Extension, which were not measured by previous experiments. Moreover, we introduce a novel method, applicable to antihydrogen hyperfine spectroscopy in a beam, that determines the zero-field hyperfine transition frequency from the two transitions measured at the same magnetic field. Our value, ▪, is in agreement with literature at a relative precision of 0.44 ppb. This is the highest precision achieved on hydrogen in a beam, improving over previous results by a factor of 6. [ABSTRACT FROM AUTHOR]

Laser site-selective spectroscopy and high-resolution absorption measurements have been used to determine 51 crystal-field energy levels for one of the Ho3+ centres in Y 2 SiO 5. This centre is denoted as Site 2 and has been tentatively assigned as the seven-fold coordinated centre. High resolution absorption measurements reveal complex hyperfine patterns that obey an approximate selection rule. The application of a magnetic field along the three optical axes reveals the presence of avoided crossings below 0.5 Tesla, in both the ground and excited states. • Identification of energy levels of Ho3+ in Y 2 SiO 5. • Observation and modelling of magnetic hyperfine structure in absorption. • Approximate selection rules for hyperfine transitions in low symmetry sites. [ABSTRACT FROM AUTHOR]

Nuclear Magnetic Resonance (NMR) spectroscopy is the ideal tool to address the structure, reactivity and dynamics of both inorganic and biological substances. The knowledge of nuclear spin interaction and spin dynamics is increasingly consolidated, and this allows for tailoring pulse sequences. When dealing with paramagnetic systems, several decades of research have led to the development of rule-of-the-thumb criteria for optimizing the experiments, allowing for the detection of nuclei that are in very close proximity to the metal center. In turn, the observation of these systems, coupled with the development of robust and accessible quantum chemical methods, is promising to provide a link between the spectra and the structural features through the interpretation of the electronic structure. In this review, we list the challenges encountered and propose solutions for dealing with paramagnetic systems with the greatest satisfaction. In our intentions, this is a practical toolkit for optimizing acquisition and processing parameters for routine experiments aimed at detecting signals influenced by the hyperfine interaction. The implications of paramagnetic shift and line broadening are examined. With this endeavor, we wish to encourage non-expert users to consider the application of paramagnetic NMR to their systems.

Two isomeric 2-bromomethylpyridine Cu(II) complexes [Cu(C6H9NBr)2(NO3)2] with 2-bromo-5-methylpyridine (L1) and 2-bromo-4-methylpyridine (L2) were synthesized as air-stable blue materials in good yields. The crystal structures were different with [Cu(L1)2(NO3)2] (CuL1) crystallizing in the monoclinic space group P21/c, while the 4-methyl derivative CuL2 was solved and refined in triclinic P 1 ¯ . The orientation of the Br substituents in the molecular structure (anti (CuL1) vs. syn (CuL2) conformations) and the geometry around Cu(II) in an overall 4 + 2 distorted coordination was very different with two secondary (axially elongated) Cu–O bonds on each side of the CuN2O2 basal plane in CuL1 or both on one side in CuL2. The two Br substituents in CuL2 come quite close to the Cu(II) centers and to each other (Br⋯Br ~3.7 Å). Regardless of these differences, the thermal behavior (TG/DTA) of both materials is very similar with decomposition starting at around 160 °C and CuO as the final product. In contrast to this, FT-IR and Raman frequencies are markedly different for the two isomers and the UV–vis absorption spectra in solution show marked differences in the π–π* absorptions at 263 (CuL2) or 270 (CuL1) nm and in the ligand-to-metal charge transfer bands at around 320 nm which are pronounced for CuL1 with the higher symmetry at the Cu(II) center, but very weak for CuL2. The T-dependent susceptibility measurements also show very similar results (µeff = 1.98 µB for CuL1 and 2.00 µB for CuL2 and very small Curie–Weiss constants of about −1. The EPR spectra of both complexes show axial symmetry, very similar averaged g values of 2.123 and 2.125, respectively, and no hyper-fine splitting. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of the Co7Te8 layered compound have been studied for the first time using X-ray diffraction, measurements of the magnetic susceptibility, and nuclear magnetic resonance spectroscopy on 59Co nuclei. The nuclear magnetic resonance study of Co7Se8 selenide with the same structural type (NiAs) as Co7Te8 has also been performed for the first time. In contrast to Co7Se8, the ordering of vacancies and Co atoms in cation layers is absent in the Co7Te8 compound, and its crystal structure is more planar and is characterized by a significantly smaller ratio c0/a0 compared to Co7Se8 (a0 and c0 are the basic lattice parameters of NiAs). The components of the magnetic shift and electric field gradient tensors at the location of Co nuclei have been determined. A significant local charge and spin inhomogeneity of the co-mpounds has been revealed. The hyperfine coupling constant in Co ions has been estimated from the te-mperature dependences of the shift and susceptibility in Co7Te8. An anisotropic increase in the interatomic distances does not increase the localization of electrons and does not lead to the appearance of magnetic moments on Co atoms in Co7Te8. This compound remains a Pauli paramagnet down to the lowest tempe-ratures. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of the Co7Te8 layered compound have been studied for the first time using X-ray diffraction, measurements of the magnetic susceptibility, and nuclear magnetic resonance spectroscopy on 59Co nuclei. The nuclear magnetic resonance study of Co7Se8 selenide with the same structural type (NiAs) as Co7Te8 has also been performed for the first time. In contrast to Co7Se8, the ordering of vacancies and Co atoms in cation layers is absent in the Co7Te8 compound, and its crystal structure is more planar and is characterized by a significantly smaller ratio c0/a0 compared to Co7Se8 (a0 and c0 are the basic lattice parameters of NiAs). The components of the magnetic shift and electric field gradient tensors at the location of Co nuclei have been determined. A significant local charge and spin inhomogeneity of the co-mpounds has been revealed. The hyperfine coupling constant in Co ions has been estimated from the te-mperature dependences of the shift and susceptibility in Co7Te8. An anisotropic increase in the interatomic distances does not increase the localization of electrons and does not lead to the appearance of magnetic moments on Co atoms in Co7Te8. This compound remains a Pauli paramagnet down to the lowest tempe-ratures. [ABSTRACT FROM AUTHOR]

Internally contracted multireference coupled-cluster (icMRCC) theory is extended to the computation of first-order properties (expectation values). We use the previously defined Lagrange formulation of the energy functional to derive the required equations for the Lagrange multipliers and arrive at an expression for first-order properties according to the generalized Hellmann-Feynman theorem, analogous to single-reference coupled-cluster theory. The present formulation does not include orbital relaxation, but in line with previous experience in coupled-cluster theory, the single-excitation cluster operator can recover a significant portion of orbital relaxation. Further aspects of the theory that arise from the internal contraction approach are discussed. Using automated derivation techniques, we have implemented a pilot code for icMRCCSD and icMRCCSDT for testing the method numerically. We find good agreement with full configuration interaction for several properties of boron monohydride and dipole moment curves of hydrogen fluoride and chromium hydride. A particular focus is given to spin-dependent properties: The hyperfine coupling tensors of Σ and Π radicals have been computed and compared to experiment and previous computations. We discuss the problem of describing spin polarization with properly spin-adapted wavefunctions, which requires either including pseudo-triple excitations or employing sufficiently flexible reference functions. [ABSTRACT FROM AUTHOR]

Magnetic molecules have shown great potential in quantum information processing due to the chemical tunablity of their quantum behaviors. Chemical derivatives of endohedral nitrogen fullerenes with long coherence time and rich energy levels were synthesized and studied to demonstrate the ability of multiprocessing in quantum information using electron magnetic resonance. After initialization of the 12‐levelled spin system, subgroups of spin energy levels coursed by the hyperfine couplings can be selectively manipulated. The cooperatively combining of the parallel calculations enabled quantum error correction, increasing the correct rate by up to 17.82 %. Also, different subgroups of transitions divided by hyperfine coupling can be treated as independent qubits, and multi‐task quantum computing were realized by performing Z‐gate and X‐gate simultaneously, which accelerates the overall gating speed. [ABSTRACT FROM AUTHOR]

M-type Barium hexaferrite is a famous hard magnetic material with a hexagonal crystal structure. La substituted Barium hexaferrite, Ba(1-x)La(x)Fe12O19, (where, x = 0.25 and 0.30) were synthesized using ball milling followed by sintering at 1300 °C for 5 hours. X-ray diffraction patterns reveal the formation of a single-phase magnetoplumbite structure of barium hexaferrite, which belongs to the P63/mmc space group. Mossbauer spectroscopic studies were carried out to study the magnetic phase, the effect of La doping on the valency of the Fe atom, and charge distribution in the prepared samples. Mossbauer spectra is fitted using 5 sextets, shows there is 5 sublattices present in the system. From the fitting of Mossbauer spectrum, it is observed that, there is no formation of Fe2+ ion even if the doping levels are as high as 30%, as it is expected that Fe3+ ion changes its valance to maintain the charge neutrality. However, there is an increase in s-electron density for number of sites with doping. Quadrupole splitting values shows spherical charge distribution for all the sublattices except 2b, due to asymmetric nature of bipyramidal site. Slightly varied magnetic hyperfine splitting values are observed for 12 k and 4f1 sites shows the effect of La substitution. [ABSTRACT FROM AUTHOR]

We describe the synthesis, characterization, and application of an isotopologue of the trityl radical OX071, labeled with 13C at the central carbon (13C1). This spin probe features large anisotropy of the hyperfine coupling with the 13C1 (I = 1/2), leading to an EPR spectrum highly sensitive to molecular tumbling. The high biocompatibility and lack of interaction with blood albumin allow for systemic delivery and in vivo measurement of tissue microviscosity by EPR. [ABSTRACT FROM AUTHOR]

A single-seed, module-based compact laser system is demonstrated on a transportable 87 Rb -based high-precision atomic gravimeter. All the required laser frequencies for the atom interferometry are provided by free-space acousto-optic modulators (AOMs) and resonant electro-optic phase modulators (EOMs). The optical phase-locked loop between the two optical paths derived from the same laser provides an easy frequency manipulation between two laser frequencies separated by the hyperfine frequency of 6.835 GHz using an AOM and an EOM, respectively. Our scheme avoids parasite Raman transitions present in the direct EOM modulation scheme (modulating directly at the frequency of the hyperfine splitting), which have detrimental effects on the accuracy of the gravity measurements. The optical phase-locked loop also provides a convenient way for vibration compensation through the Raman lasers' phase offset. Furthermore, the modular design approach allows plug-and-play nature on each individual optic module and also increases the mechanical stability of the optical systems. We demonstrate high-precision gravity measurements with 17.8 μ Gal stability over 250 s averaging time and 2.5 μ Gal stability over 2 h averaging time. [ABSTRACT FROM AUTHOR]

Breast cancer is one of the major types of cancer around the world, and early diagnosis is essential for successful treatment. New contrast agents (CAs), with reduced toxicology, are needed to improve diagnosis. One of the most promising Magnetic Resonance Imaging (MRI) CA is based on rhenium conjugated with a benzothiazole derivate (ReABT). In this sense, DFT has been used to evaluate the best methodology for calculating the hyperfine coupling constant (Aiso) of ReABT. Then, a thermodynamic analysis was performed to confirm the stability of the complex. Furthermore, a docking study of ReABT at the enzyme PI3K active site and Aiso calculations of ReABT in the enzyme environment were carried out. The best methodology for the Aiso calculation of ReABT was using the M06L functional, SARC-ZORA-TZVP (for Re) and TZVP (for all other atoms) basis set, relativistic Hamiltonian, and the CPCM solvation model with water as the solvent which confirm that the relativistic effects are important for calculating the Aiso values. In addition, thermodynamic analysis indicates that ReABT presents a higher stability and a lower toxicity than Gd-based CAs. The docking studies point out that ReABT interacts with amino acids residues of alanine, aspartate, and lysine from the PI3K active site. Considering the enzyme environment, Aiso values decrease significantly. These findings indicate that the CA candidate ReABT could be a good candidate for a new contrast agent. [ABSTRACT FROM AUTHOR]

Muons are puzzling physicists since their discovery when they were first thought to be the meson predicted by Yukawa to mediate the strong force. The recent result at Fermilab on the muon g-2 anomaly puts the muonic sector once more under the spotlight and calls for further measurements with this particle. Here, we present the results of the measurement of the 2S1/2, F = 0 → 2P1/2, F = 1 transition in Muonium. The measured value of 580.6(6.8) MHz is in agreement with the theoretical calculations. A value of the Lamb shift of 1045.5(6.8) MHz is extracted, compatible with previous experiments. We also determine the 2S hyperfine splitting in Muonium to be 559.6(7.2) MHz. The measured transition being isolated from the other hyperfine levels holds the promise to provide an improved determination of the Muonium Lamb shift at a level where bound state QED recoil corrections not accessible in hydrogen could be tested. This result would be sensitive to new physics in the muonic sector, e.g., to new bosons which might provide an explanation of the g-2 muon anomaly and allow to test Lorentz and CPT violation. We also present the observation of Muonium in the n = 3 excited state opening up the possibility of additional precise microwave measurements. Muonium is a hydrogen like bound system with a positive muon and an electron. Here the authors measure the Lamb shift and frequency of the transition from 2S1/2, F = 0 state to 2P1/2, F = 1 state in muonium atom and the hyperfine structure of the 2S level. [ABSTRACT FROM AUTHOR]

The intermetallic phases APd2Zn3 (A=Ca, Sr, Eu) were synthesized from the elements in sealed niobium ampules in an induction furnace. The phase purity of the samples was checked by powder X‐ray diffraction (Guinier technique). The structures were refined from single crystal X‐ray diffractometer data: YNi2Al3 type (CaCu5 superstructure), P6/mmm, a=936.97(4), c=420.75(2) pm, wR2=0.0206, 259 F2 values, 17 variables for CaPd2Zn3, a=953.63(6), c=425.38(3) pm, wR2=0.0185, 230 F2 values, 17 variables for SrPd2Zn3 and a=948.20(7), c=423.20(3) pm, wR2=0.0209, 228 F2 values, 18 variables for EuPd2.12(1)Zn2.88(1). The europium‐based crystal showed a small homogeneity range through Pd/Zn mixing. The striking structural motifs of the APd2Zn3 phases are Kagome networks formed by the palladium and zinc atoms. The superstructure formation (discussed on the basis of a Bärnighausen tree) results from a different Pd/Zn coloring and a shift of one A position by c/2. The divalent character of europium in EuPd2Zn3 was substantiated by magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements. EuPd2Zn3 orders ferrimagnetically at TC=17.5(5) K. The magnetization behavior at 3 K (two‐step magnetization) confirms the existence of two crystallographically independent europium sites. The 151Eu Mössbauer spectrum at 5 K shows full magnetic hyperfine field splitting (δ=−8.99(4) mm s−1 and BHf=27.7(1) T). [ABSTRACT FROM AUTHOR]

Based on cesium 6S1/2—6P3/2—6D5/2 (852 nm + 917 nm) ladder-type system, we simultaneously obtain the Doppler-free saturated absorption spectroscopy (SAS) between the 6S1/2 → 6P3/2 transition and optical–optical double resonance (OODR) spectroscopy between the 6P3/2 → 6D5/2 transition, when the frequency of 852 nm laser is scanned over the lower transition while keeping the 917 nm laser resonant on the upper transition. The SAS as a frequency scale is used to measure the frequency intervals of hyperfine splitting of the 6D5/2 excited state via the OODR spectra. With the measured values of hyperfine splitting, the hyperfine coupling constants of the 6D5/2 state are determined as magnetic dipole Ahfs = − 4.60 (5) MHz and electric quadrupole Bhfs = 0.23 (47) MHz, which are consistent with previous results. A simple and self-calibration method of measuring the unknown hyperfine structure of an excited state using its own known hyperfine splitting of another state is demonstrated without the aid of any extra frequency calibration tools. [ABSTRACT FROM AUTHOR]

The magnesium-rich intermetallic compounds RE3Ag4Mg12 (RE = Y, La–Nd, Sm–Dy, Yb) and AE3Ag4Mg12 (AE = Ca, Sr) were synthesized from the elements in sealed tantalum ampoules through heat treatment in an induction furnace. X-ray powder diffraction studies confirm the hexagonal Gd3Ru4Al12 type structure, space group P63/mmc. Three structures were refined from single crystal X-ray diffractometer data: a = 973.47(5), c = 1037.19(5) pm, wR2 = 0.0296, 660 F2 values, 30 variables for Gd3Ag3.82(1)Mg12.18(1), a = 985.27(9), c = 1047.34(9) pm, wR2 = 0.0367, 716 F2 values, 29 variables for Yb3Ag3.73(1)Mg12.27(1) and a = 992.41(8), c = 1050.41(8) pm, wR2 = 0.0373, 347 F2 values, 28 variables for Ca3Ag3.63(1)Mg12.37(1). Refinements of the occupancy parameters revealed substantial Ag/Mg mixing within the silver-magnesium substructure, a consequence of the Ag@Mg8 coordination. The alkaline earth and rare earth atoms build Kagome networks. Temperature dependent magnetic susceptibility measurements indicate diamagnetism/Pauli paramagnetism for the compounds with Ca, Sr, Y and YbII, while the others with the trivalent rare earth elements are Curie-Weiss paramagnets. Most compounds order antiferromagnetically at TN = 4.4(1) K (RE = Pr), 34.6(1) K (RE = Gd) and 23.5(1) K (RE = Tb) while Eu3Ag4Mg12 is a ferromagnet (TC = 19.1(1) K). 151Eu Mössbauer spectra confirm divalent europium (δ = −9.88(1) mm s−1). Full magnetic hyperfine field splitting (18.4(1) T) is observed at 6 K. Yb3Ag4Mg12 shows a single resonance in its 171Yb solid state NMR spectrum at 6991 ppm at 300 K indicating a strong, positive Knight shift. [ABSTRACT FROM AUTHOR]

Color centers in wide-bandgap semiconductors, including diamond and silicon carbide (SiC), are attractive systems for quantum information and quantum sensor devices with excellent spin properties at room temperature. In addition, nuclear spins in crystals are expected to serve as the quantum memory and to enhance the sensitivity of quantum sensors with the combination with color centers as a result of an extremely long spin coherence time. Although the spin state of both color centers and nuclear spins coupled through hyperfine interactions is usually optically read out, an electrical readout technique is important for miniaturizing and integrating devices. In the present study, we report the electrical detection of silicon vacancy (V2) centers in 4H-SiC by photocurrent-detected magnetic resonance (PDMR) using a frequency-sweep technique. We electrically observe the spin coherence of the V2 centers and clearly resolve the hyperfine splitting of the electron spin signal for the V2 centers coupled with next-nearest-neighbor 29Si atoms. In addition, we apply PDMR to electron–nuclear double resonance (PD-ENDOR) to detect nuclear magnetic resonance of 29Si at room temperature and find that this method can resolve nuclear spins coupled with neighboring electron spins in the V2 centers. The realization of PD-ENDOR is expected to be a critical step toward the development of electrically driven integrated quantum devices. [ABSTRACT FROM AUTHOR]

Negative ions are important in many areas of science and technology, e.g., in interstellar chemistry, for accelerator-based radionuclide dating, and in anti-matter research. They are unique quantum systems where electron-correlation effects govern their properties. Atomic anions are loosely bound systems, which with very few exceptions lack optically allowed transitions. This limits prospects for high-resolution spectroscopy, and related negative-ion detection methods. Here, we present a method to measure negative ion binding energies with an order of magnitude higher precision than what has been possible before. By laser-manipulation of quantum-state populations, we are able to strongly reduce the background from photodetachment of excited states using a cryogenic electrostatic ion-beam storage ring where keV ion beams can circulate for up to hours. The method is applicable to negative ions in general and here we report an electron affinity of 1.461 112 972(87) eV for 16O. High-precision measurements are useful to find isotopic shifts and electron correlation. Here the authors measure electron affinity and hyperfine splitting of atomic oxygen with higher precision than previous studies. [ABSTRACT FROM AUTHOR]

EPR spectroscopy requires a combination of fixed microwave radiation and resonant external magnetic field. Bigger is not necessarily better in that low-frequency and -field EPR (LFEPR) can provide useful information as well as reduced linewidths that can allow better observation of hyperfine coupling. More importantly, LFEPR allows very low g values to be readily observed, such as often found in low-spin d5 systems. [ABSTRACT FROM AUTHOR]

High-accuracy calculations are performed for the four lowest 3 D states of the beryllium atom. All-electron explicitly correlated Gaussian (ECG) functions are employed to expand the functions and the non-relativistic internal Hamiltonian used in the calculations, which is obtained by rigorously separating out the centre-of-mass motion from the laboratory-frame Hamiltonian, explicitly depends on the finite nuclear mass of 9 Be. The nonrelativistic wave functions of the considered states of 9 Be are generated variationally with the nonlinear parameters of the Gaussians optimised using a procedure that employs the energy gradient determined with respect to these parameters. The nonrelativistic wave functions are used to calculate the leading relativistic corrections employing the perturbation theory at the first-order level. Only corrections that do not produce fine/hyperfine splitting of the energy levels are considered. The corrections are added to the nonrelativistic energies and the results are used to calculate the so-called 'centre of gravity' transition energies with respect to the 9 Be 1 S ground state. A comparison with high-quality experimental results shows agreement to within about 0.6 cm − 1 . [ABSTRACT FROM AUTHOR]

We examine the properties of ditauonium, an exotic atom consisting of a pair of opposite-sign τ leptons bound together by the quantum electrodynamics (QED) interaction in a hydrogen-like state. The energy levels, decay modes and associated partial widths, as well as total widths and lifetimes of the ortho- and para-ditauonium states are calculated. Higher-order QED effects – including Lamb shifts, hyperfine splitting structure, and partial decay widths corrections – are incorporated up to approximately next-to-next-to-leading-order (NNLO) accuracy. Beyond the dominant diphoton and difermion decays, the rates of rare decay channels – including Dalitz, radiative, triple-photon, double-Dalitz, four-fermion, and neutrinos final states – are determined. [ABSTRACT FROM AUTHOR]

The zero-point energies (ZPEs) of paramagnetic molecules, free and compressed in a C59N paramagnetic cage, were computed. The excess of energy acquired by molecules under compression depended on the deuterium and tritium isotopes which ranged from 6–8 kcal/mol for H2+ to 1.0–1.5 kcal/mol for HO• and HO2. The differences in the ZPEs of compressed isotopic molecules resulted in large deuterium and tritium isotope effects which differed for singlet and triplet spin states. The hyperfine coupling (HFC) constants for protons and 17O nuclei decreased under compression, confirming the leakage of the unpaired π-electron from the central oxygen atom of guest molecules into the system of π-electrons of the cage, and its distribution over 60 atoms of the C59N. The latter seems to be the reason why the nitrogen-14 HFCs for C59N remain almost unchanged upon encapsulation of guest molecules. The singlet-triplet splitting is shown to depend on the Coulomb interaction, which controls the sign of the exchange potential. The importance of compression effects on the functioning of enzymes as molecular compressing devices is discussed. [ABSTRACT FROM AUTHOR]

• The paramagnetic center in 2-nitrobenzoic acid single crystal was examined. • Gamma ray created a resonance structure in the carboxyl group. • The 2-nitrobenzoic acid anion radical was formed. • Paramagnetic structure was analyzed by EPR spectroscopy. 2-nitrobenzoic acid (C 7 H 5 NO 4) (2NBA) single crystals were made paramagnetic using 60Co-gamma rays. An attempt was made to detect the resonance form formed in 2-nitrobenzoic acid single crystal with Electron Paramagnetic Resonance (EPR) Spectroscopy. EPR spectra were taken at 125 K in three different axes of the crystal. As a result of EPR analysis of gamma irradiated 2NBA single crystal, it was understood that 2NBA anion radical was formed. The principal values of the hyperfine structure constants, the principal values of the g-tensor and their direction cosines were calculated. [ABSTRACT FROM AUTHOR]

We observed hyperfine-resolved high-resolution fluorescence excitation spectra of k = 0, N = 1 ← 0 transitions in 82 vibronic bands of the òB2 ← X²A1 system of 14NO2 in the 14 500-16 800 cm-1 region by crossing a jet-cooled molecular beam and a single-mode dye laser beam at right angles. We determined hyperfine interaction constants of the lower and upper states for all the observed vibronic bands based on the analysis of the hyperfine structures of k = 0, N = 1 ← 0 transitions. Most of the determined Fermi contact interaction constants were found to be distributed in 0.0013-0.0038 cm-1, which are intermediate in magnitude between those in lower and higher energy region reported by other groups. A sharp decreasing of the Fermi contact interaction constant was found in 16 200-16 600 cm-1, and it may be caused by the interaction with the dark C²A2 state. The hyperfine interaction constants are powerful clues to obtain reliable vibronic assignment. We tentatively assigned vibronic bands located at 14 836 cm-1, 15 586 cm-1, and 16 322 cm-1 as the transitions to the intrinsic (0,7,0), (0,8,0), and (0,9,0) vibrational levels of the òB2 state, respectively. [ABSTRACT FROM AUTHOR]

A general algorithm for computing the quadrupole-hyperfine effects in the rovibrational spectra of polyatomic molecules is presented for the case of ammonia (NH3). The method extends the general variational approach TROVE [J. Mol. Spectrosc. 245, 126-140 (2007)] by adding the extra term in the Hamiltonian that describes the nuclear quadrupole coupling, with no inherent limitation on the number of quadrupolar nuclei in a molecule. We applied the new approach to compute the nitrogen-nuclearquadrupole hyperfine structure in the rovibrational spectrum of 14NH3. These results agree very well with recent experimental spectroscopic data for the pure rotational transitions in the ground vibrational and ν2 states and the rovibrational transitions in the ν1, ν3, 2ν4, and ν1 + ν3 bands. The computed hyperfine-resolved rovibrational spectrum of ammonia will be beneficial for the assignment of experimental rovibrational spectra, further detection of ammonia in interstellar space, and studies of the proton-to-electron mass variation. [ABSTRACT FROM AUTHOR]

In this study, the superoxide radical O2•− formed by treating Ti(OR)4 (R = iPr, nBu) with H2O2 in the presence of KOH was detected in the EPR spectra. The g-tensor of this radical differs from the typical values reported for a superoxide on various TiO2 surfaces. On the other hand, similar g-tensor components g||(zz = 2.10 ± 0.01, g⊥ = 2.005 ± 0.003 assigned to the O2•− were previously observed for radicals in aqueous solutions in the presence of K2O, alkaline solutions of DMSO, and water/DMSO mixtures. A common factor in all these systems is the presence of alkali ions. However, there was no structural support for the possible interaction of alkali ions with a superoxide in these systems. The use of multifrequency pulsed EPR techniques in this work revealed the stabilization of the O2•− near the K+ ion and its involvement in a strong hydrogen bond with the surface. These findings are consistent with the features previously reported for superoxides on a Na pre-covered MgO surface. Interactions with a closely located 23Na and a strongly coupled 1H proton were also seen in the HYSCORE spectra but assigned to two different superoxides with various gzz values presented in the sample.

[Display omitted] • First microwave spectrum measurements for the butadiene ruthenium tricarbonyl complex. • Extensive high level calculations on the molecular structure and nuclear quadrupole coupling for this complex. • First resolved and analysed 101Ru and 99Ru quadrupole coupling spectra in a molecule. • Core potential (ECP) basis sets give better structures; all-electron basis sets give better quadrupole calculations. The microwave spectrum of η4-butadiene ruthenium tricarbonyl was measured in the 5–15 GHz frequency range using a Flygare-Balle type pulsed beam Fourier transform microwave (FTMW) spectrometer. The rotational constants for the 102Ru isotopologue were determined to have the following values: A = 932.20099(42), B = 858.03248(47) and C = 831.35161(37) MHz. The centrifugal distortion constant d J is 0.0862(29)kHz. 22 a-dipole and 4c-dipole transitions were measured. Extensive high-level G16 calculations were made using DFT and MP2 methods with various basis sets, some including core-potentials (ECP). The best structure was calculated with Gaussian 16 using B3LYP/def2-QZVPP, which includes a core potential (ECP). Extensive all-electron calculations were made based on the best ECP structure to predict 101Ru and 99Ru quadrupole coupling strengths. Quadrupole hyperfine structure splittings were measured for both 101Ru and 99Ru. The hyperfine structure splittings for the 101Ru nuclear quadrupole were measured, yielding the values of 1.5χ aa = 98.12(17) MHz and 0.25(χ bb -χ cc) = 36.059(30). Measured hyperfine structure splittings for 99Ru quadrupole coupling yielded the values of 1.5χ aa = 16.99(77) MHz and 0.25(χ bb -χ cc) = 6.23(32). These values are in reasonable agreement with some of the all-electron calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • The rotational spectrum of 1,1-dichloro-1-silacyclohex-2-ene is reported for the first time. • The hyperfine splitting has been adequately deconvoluted, allowing for meaningful analysis of the quadrupole coupling. • The determined structural parameter values correspond well to other chlorinated silanes. The ground state rotational spectrum of 1,1-dichloro-1-silacyclohex-2-ene has been recorded using a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. Several isotopologues in their natural abundances have been observed in the free-jet expansion, and their spectra assigned, making it possible to present a partial heavy-atom substitution structure. Furthermore, the high resolution of this technique allows the complicated hyperfine splitting pattern to be largely deconvoluted. As a result, the on-diagonal nuclear quadrupole coupling constants for the two chlorine atoms have been determined for all observed isotopologues. Additionally, χ bc is determined for both chlorine atoms of the parent species. The quadrupole coupling tensors for the parent species have been diagonalised, noting some assumptions have been made pertaining to the off-diagonal nuclear quadrupole coupling constants in the principal axis system, to yield reasonable values of χ zz and η which are then compared. [ABSTRACT FROM AUTHOR]

Graphical depiction of LUMOs of cis and trans isomers of VO(acac) 2 pyr complexes in oxidized state, and corresponding SOMOs of the reduced state. [Display omitted] The use of vanadium complexes for potential applications in medicine largely depends on the structural properties of the complex itself, as well as on the electronic configuration of the metal and its oxidation state. When the vanadium complex binds to biomolecules or by binding solvent molecules to the complex, there is a change in the structure but also a change in the redox properties of the complex. Using theoretical methods, especially Density Functional theory (DFT), it is possible to determine which factors influence changes in the redox properties of the complex. Furthermore, by calculating the Electron Paramagnetic Resonance (EPR) constants of hyperfine coupling, it is possible to obtain not only data on the electronic configuration, but also to predict changes in redox properties upon changes in the structure of the complex. DFT results show that the binding of pyridine or imidazole to the VO(acac) 2 complex leads to a lowering of the redox potential. The largest changes in the redox potential were observed in the case when the incoming ligand binds in a cis position relative to the V O bond. [ABSTRACT FROM AUTHOR]

The intermolecular hyperfine relaxation-induced dipolar modulation enhancement (ih-RIDME) experiment has a promising potential to quantitatively characterize the nuclear environment in the 0.8-3 nm range around an electron spin. Such information about the spatial arrangement of nuclei is of great interest for structural biology as well as for dynamic nuclear polarization (DNP) methods. In order to develop a reliable and sensitive spectroscopic tool, a solid data model needs to be established. Here, we attempt to provide a theoretical explanation for the experimentally observed properties of the ih-RIDME signal. Our main approach uses a perturbation expansion of the Baker–Campbell–Hausdorff formula during the transverse evolution of the electron spin, treating the nuclear dipolar Hamiltonian as a perturbation. We show that a product structure of the ih-RIDME signal follows directly from the statistical independence of the perturbation terms and the multinuclear hyperfine coupling, and that this signal composition is expected when the mixing time exceeds the 95% decay of the Hahn echo. [Display omitted] • Homonuclear couplings contribute to the RIDME background beyond the mixing block. • Homonuclear couplings are treated as a perturbation in BCH formula. • Perturbation analysis reduces a many-spin problem to a set of numerical descriptors. • Hyperfine field and nuclear perturbation descriptors are statistically independent. • Statistical independence gives rise to a factor composition of ih-RIDME traces. [ABSTRACT FROM AUTHOR]

We report high-resolution measurements and analysis of the optical transmission and emission spectra of a concentration series of La (1- x) Pr x AlO 3 (x = 10−3, 9 ⋅ 10−3, and 2 ⋅ 10−2) single crystals in a wide frequency range ((2-27) ⋅ 103 cm−1) at temperatures 5–300 K, below the structural phase transition from the cubic P m 3 ‾ m to the rhombohedral R 3 ‾ c phase. Pr3+ ions substitute for La3+ ions at sites with point symmetry D 3. All recorded spectral lines are assigned to specific initial and final crystal-field (CF) energy levels, the scheme of CF levels is constructed and described by an appropriate set of CF parameters. The structural phase transition is accompanied by shear strains and the formation of ferroelastic twin domains of four types compressed along one of the four C 3 axes in the parent cubic crystal lattice. Specific features of the measured spectra, namely, anomalous broadening of spectral lines and doublet structure of some lines corresponding to transitions between CF singlets and doublets, are considered as a result of interaction of 4 f electrons with the field of random shear deformations competing at the boundaries of twin domains. Modeling of the observed line shapes was performed taking into account both hyperfine interactions and random lattice strains, as well as the effect of temperature. The width (6.6 ± 0.7)⋅10− 4 of the introduced two-dimensional distribution function of random strains was found from a comparison of simulated and measured profiles of the split spectral lines. The results of this work can be applied for quantitative assessment of crystal quality. • High-resolution absorption and luminescence spectra of LaAlO 3 :Pr3+ were obtained. • Сrystal-field parameters for Pr3+ in LaAlO 3 were found based on spectra analysis. • Boundaries of ferroelastic twin domains are a source of random lattice strains. • Shape of spectral lines is modeled considering hyperfine structure and random strains. • Modeling takes into account the effect of temperature on the line shape. [ABSTRACT FROM AUTHOR]

In order to take advantage of the strong correlation between geometric changes and electronic properties, better understanding of the structure and properties of perovskites doped with paramagnetic transition metal ions is required. Computational characterization of these dopants and calculated hyperfine values provide a guide that can ultimately aid in the interpretation of experimentally obtained electron paramagnetic resonance (EPR) spectra. In this study, we perform ab initio calculation of the hyperfine splitting parameter for Sr-substituted Mn2+ in SrTiO3 in various geometries in order to assign experimentally reported EPR peaks to exact dopant structures. Additionally, we calculate the hyperfine parameters for Mn4+ and Mn2+∕4+ with adjacent oxygen vacancy, which remain to be assigned peaks in experimental EPR spectra. Calculation of Ti-substituted Mn is largely hindered by the highly correlated electronic structure; however, it is shown that reasonable hyperfine values for Ti-site defects can be obtained by tuning functional parameters. Overall, this study demonstrates that calculating the hyperfine splitting for a transition metal dopant in a complex oxide is feasible and can provide a fingerprint for different geometries in equivalently defected systems. [ABSTRACT FROM AUTHOR]

Concentration variation of Mn2+ ions doped zincaluminoborophosphate (ZnAlBP) glasses of 40 ZnO + 25 H3BO3 + (30-x) P2O5 + 5 Al2O3 + x MnO with 0 ≤ x ≤ 0.8 (x=0, 0.2, 0.4, 0.6 and 0.8) have been prepared and investigated by structural and spectroscopic techniques. The XRD diffractograms confirm the amorphous nature of the prepared samples. The FTIR spectra reveal the existence of BO3 and BO4 units along with fundamental P-O-H and B-O-H structural units in the present glass system. The Optical absorption spectra exhibit two low intensity bands centered at 407 nm (24,570 cm-1) and 689 (14,514 cm-1). These bands were assigned to 6A1g(S) → 4A1g (G) + 4Eg (G) and6A1g(S) → 4T1g (G) characteristic transitions of Mn2+ ions in octahedral symmetry. Tauc's plots were drawn to measure the optical band gaps for the direct and indirect transitions. The energy gaps show a decreasing trend for the selected ZnAlBP: Mn2+ glass system. The well-resolved hyperfine splitting EPR spectra of prepared glass samples exhibit resonance at g ≈ 1.98 indicating the Mn2+ ions are in octahedral site symmetry. The hyperfine splitting factor (hfs), the number of spin levels (N), hyperfine constant (A), zero-field splitting parameter (D), and paramagnetic susceptibility (χ) have been determined. The magnitude of g indicates the predominant ionicity in the glasses. [ABSTRACT FROM AUTHOR]

The γ-irradiated 77K samples (RaO)x(SiO2)y with adsorbed water were studied using EPR spectroscopy, and EPR spectrum with g=2.0028 and hyperfine splitting constant A(H)=505.3 G belonging to hydrogen atoms was registered. EPR, presumably attributed to paramagnetic hole (≡Si-O)+, electronic (≡Si-)- centers and products of their interaction with water molecules spectra was registered. It is assumed that the main part of atomic hydrogen was oxidized to the HO2• radical, and some of the H• atoms participate in surface radiative hydrogenation reactions with the formation of hydrogen-containing radicals when irradiated samples were heated from 77 K to room temperature. It is also assumed that •OH radicals are formed on the surface of γ--irradiated at 77K (RaO)x(SiO2)y samples. [ABSTRACT FROM AUTHOR]

Obtaining an accurate first-principle description of the electronic properties of dopant qubits is critical for engineering and optimizing high-performance quantum computing. However, density functional theory (DFT) has had limited success in providing a full quantitative description of these dopants due to their large wavefunction extent. Here, we build on recent advances in DFT to evaluate phosphorus dopants in silicon on a lattice comprised of 4096 atoms with hybrid functionals on a pseudopotential and all-electron mixed approach. Remarkable agreement is achieved with experimental measurements including: the electron-nuclear hyperfine coupling (115.5 MHz) and its electric field response (−2.65 × 10−3 μm2/V2), the binding energy (46.07 meV), excited valley-orbital energies of 1sT2 (37.22 meV) and 1sE (35.87 meV) states, and super-hyperfine couplings of the proximal shells of the silicon lattice. This quantitative description of spin and orbital properties of phosphorus dopant simultaneously from a single theoretical framework will help as a predictive tool for the design of qubits. Modelling the quantum transport properties of qubit arrays and the electronic properties of dopant qubits is computationally challenging yet crucial for device optimization in quantum computing. Here, the authors compare different DFT-based methods to describe the properties of shallow donor-based qubits in silicon. [ABSTRACT FROM AUTHOR]

The relaxation time of a single-electron spin is an important parameter for solid-state spin qubits, as it directly limits the lifetime of the encoded information. Thanks to the low spin-orbit interaction and low hyperfine coupling, graphene and bilayer graphene (BLG) have long been considered promising platforms for spin qubits. Only recently, it has become possible to control single-electrons in BLG quantum dots (QDs) and to understand their spin-valley texture, while the relaxation dynamics have remained mostly unexplored. Here, we report spin relaxation times (T1) of single-electron states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times exceeding 200 μs at a magnetic field of 1.9 T. The T1 values show a strong dependence on the spin splitting, promising even longer T1 at lower magnetic fields, where our measurements are limited by the signal-to-noise ratio. The relaxation times are more than two orders of magnitude larger than those previously reported for carbon-based QDs, suggesting that graphene is a potentially promising host material for scalable spin qubits. Graphene has long been considered to be a promising host for spin qubits, however a demonstration of long spin relaxation times for a potential qubit has been lacking. Here, the authors report the electrical measurement of the single-electron spin relaxation time exceeding 200 μs in a bilayer graphene quantum dot. [ABSTRACT FROM AUTHOR]

We describe a new sub-Doppler spectrometer with an enlarged gas cell, which was created at the IAP RAS for high-precision laboratory measurements of molecular transitions at millimeter and submillimeter wavelengths in the interests of radio astronomy. By using a larger diameter with a shortened cell length, a calibrated attenuator for radiation power adjustment, and synthesizers with lower phase noise, it was possible to eliminate a number of shortcomings of the previous spectrometer and not only to measure with high accuracy the transition frequencies of a number of molecules taking into account hyperfine splitting, but also to study their shifts due to both pressure and radiation power. In particular, information about precise frequencies will be used to examine the inner dynamics in the star-forming regions, and also to search for variations of fundamental constants. The principle of frequency-independent cell-aperture irradiation was employed when the optical scheme of the spectrometer was designed. The examples show Lamb-dip measurements of the hyperfine structure in the CH3CN and HNCO molecular lines. [ABSTRACT FROM AUTHOR]

Precision atomic spectroscopy provides a solid model independent bound on the existence of new dark forces among the atomic constituents. We focus on the keV-GeV region investigating the sensitivity to such dark sectors of the recent measurements on muonic atoms at PSI. To this end we develop for the first time, the effective field theory that describes the leading effect of a new (pseudo-)vector or a (pseudo-)scalar particle of any mass at atomic energies. We identify in the Lamb Shift measurement in muonic deuterium (μD) and the 2s Hyperfine Splitting (HFS) in muonic hydrogen (μH) the most promising measurements to probe respectively spin-independent and spin-dependent new forces. Furthermore, we evaluate the expression of the vector force HFS finding that a future measurement of the 2s HFS in regular hydrogen could provide the strongest atomic bound for such a force for masses above 100 MeV. [ABSTRACT FROM AUTHOR]

Graphene nanoflakes have attracted a growing interest owing to their tunable and unique electronic, optical, and magnetic properties. In particular, recent breakthroughs in the on-surface synthesis and characterization of graphene nanoflakes exhibiting π -magnetism have shown their promising great potential for spintronic applications. In this context, a theoretical investigation on the relative energetic stability, 13C nuclear magnetic resonance (NMR) chemical shifts, magnetically induced currents, hyperfine shifts, and hyperfine coupling constants of graphene nanoflakes of hexagonal and triangular shape has been performed using the density functional theory (DFT). The role played by the size, shape, and atomic site position in the flake on the 13C isotropic chemical shift is thoroughly examined. As a general trend, considering only the orbital contribution, sites from the innermost region of the flake present lower chemical shifts than the ones close to the border and, for large enough systems, such values tend to converge to roughly the graphene one. For the open-shell flakes, the hyperfine shifts and coupling constants exhibit oscillatory behavior, with opposite signs for adjacent sites. The magnitude of these parameters is progressively reduced with the increase in the distance from the edge, where the largest values of excess spin density are concentrated. [Display omitted] ● NMR parameters of graphene nanoflakes are investigated through DFT based simulations. ● Flakes of different sizes and shapes (coronoids and triangulenes) are analyzed. ● Spin-state energy splittings and spin ground state are calculated for triangulenes. ● 13C NMR chemical shifts for coronoids show good correlation with the flake size and atomic site position. ● Spin density and hyperfine shifts show oscillatory behavior for adjacent sites in triangulenes. [ABSTRACT FROM AUTHOR]