Hyperfine Constants Research Articles

Hyperfine analysis of the (2, 0) [18.3]3-X3Δ3 transition of cobalt monoboride

High-resolution laser-induced fluorescence spectra of the (2, 0) [18.3]3-X3Δ3 transition of cobalt monoboride (CoB) have been recorded. We report updated rotational parameters for both the [18.3]3 (v′ = 2) and X3Δ3 (v″ = 0) states of Co11B, as well as newly determined hyperfine interaction parameters. The observed hyperfine splitting is mainly due to the nuclear spin of 59Co (I = 7/2, μ/μN = 4.627); the 11B (I = 3/2, μ/μN = 2.689) interaction only results in broadening of the individual hyperfine transitions. The magnetic hyperfine constants help confirm the ground state electronic configuration, (8σ)2(3π)4(1δ)3(9σ)1, and provide more insight into the configurational mixing in the excited state.

Vanadium in yttrium aluminum garnet: Charge states and localization in the lattice

Incorporation of the V3+ and V4+ ions into the yttrium aluminum garnet Y3Al5O12 (YAG) lattice has been studied by the correlated optical absorption and electron paramagnetic resonance (EPR) measurements. Only the V3+ ions at both octahedral and tetrahedral aluminum sites are found in as-grown crystals. However, annealing in air leads to the transformation of the V3+ to V4+, whereas annealing in the hydrogen atmosphere remains the V3+ concentration almost unchanged. Spin Hamiltonian parameters of the V3+ and V4+ ions at the tetrahedral sites including the zero field splitting and 51V hyperfine constants are determined using high-frequency, up to 300 GHz, EPR measurements. By using the spin Hamiltonian parameters, the ground state energy levels splitting of the V3+ and V4+ ions were calculated in the framework of the crystal field theory. The g and hyperfine tensors suggest that electron density around the tetrahedral V3+ ion is distributed strongly inhomogeneously resulting also in large (40%) reduction of the spin-orbit coupling constant whereas the tetrahedral V4+ ion exhibits weaker covalent bounding with surrounding ligands. Furthermore, the obtained EPR data on vanadium ions allow to improve identification of the optical absorption peaks in YAG:V crystals.

Insight of the Metal-Ligand Interaction in f-Element Complexes by Paramagnetic NMR Spectroscopy.

The magnetic properties of LnIII and AnIII complexes formed with dipicolinate ligands have been studied by NMR spectroscopy. To know precisely the geometries of these complexes, a crystallographic study by single-crystal X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) in solution was performed. Several methods to separate the paramagnetic shifts observed in the NMR spectra were applied to these complexes. Methods using a number of nuclei of the dipicolinate ligands revealed an abrupt change in the geometries of the complexes and a metal-ligand interaction in the middle of the lanthanide series. A study of the variation of the paramagnetic shifts with temperature demonstrated that higher-order terms of the dipolar and contact contributions are required, especially for the lightest LnIII and almost all the studied AnIII . Bleaney's parameters <Sz >a and relating to the contact and dipolar terms, respectively, were deduced from experimental data and compared with the results of ab initio calculations. Quite a good agreement was found for the temperature dependencies of <Sz >a and . However, the values obtained from cation magnetic anisotropy calculations showed some discrepancies with the values derived from Bleaney's equation defined for LnIII . Other parameters, such as the crystal field parameter and the hyperfine constants Fi obtained from the experimental data of the [An(ethyl-dpa)3 ]3- complexes (ethyl-dpa=4-ethyl-2,6-dipicolinic acid), are at odds with the assumptions underlying Bleaney's theory.

The pure rotational spectrum of the ZnBr radical (X2Σ+): Trends in the zinc halide series.

The pure rotational spectrum of ZnBr (X2Σ+) has been recorded in the frequency range 259-310 GHz using millimeter-wave direct absorption techniques. This study is the first quantitative spectroscopic investigation of this free radical. ZnBr was synthesized in a DC discharge by the reaction of zinc vapor in argon with one of three reagents: BrCH3, Br2CH2, or Br2. Eight rotational transitions were measured for six isotopologues (64Zn79Br, 64Zn81Br, 66Zn79Br, 66Zn81Br, 68Zn79Br, and 68Zn81Br), all of which exhibited spin-rotation interactions. Furthermore, transitions originating in the v = 1 through 3 excited vibrational states were obtained for certain isotopologues. Five rotational transitions were also recorded for 67Zn79Br, in which hyperfine splittings were observed arising from the 67Zn nucleus (I = 5/2). The spectra were analyzed using a Hund's case (bβJ) Hamiltonian, and rotational, spin-rotation, and 67Zn magnetic hyperfine constants were determined. Equilibrium parameters were also derived for the 64Zn79Br, 64Zn81Br, 66Zn79Br, and 66Zn81Br isotopologues, including the vibrational constant, ωe = 286 cm-1. The equilibrium bond length was derived to be re = 2.268 48(90) Å. Analysis of the 67Zn hyperfine parameters suggest a decrease in ionic character in ZnBr from the other known zinc halides, ZnF and ZnCl.

Revised energy levels and hyperfine structure constants of Ta I

A wave number calibrated Fourier transform spectrum, extending from the UV-region (211 nm) to the infrared region (4.6 µm), was used to determine with high accuracy the center of gravity wave numbers of hyperfine structure - resolved Ta I spectral lines. The majority of the hyperfine constants, necessary for this step, were known from literature. For some energy levels, the constants were determined in this work. From the obtained wave numbers of altogether 3249 spectral lines, we calculated in a global fit procedure the energies of 216 levels with even parity and 290 levels with odd parity. A comparison between our results and (partially unpublished) energy values from the literature is given, as well as a compilation of available hyperfine structure constants.

The relativistic computations of spectral lines of 129Xe I

Abstract In this paper, we present our achievement on the relativistic computations of the spectral lines for the levels belonging to the 6s[k]J, 4f[k]J, 5d[k]J, 6p[k]J, 7s[k]J, 5f[k]J, 6d[k]J, 7p[k]J and 8s[k]J intermediate Rydberg series in the heavy xenon-129 isotope. These spectral lines are identified by the energy levels, the transition rates, the oscillator strengths, the Lande gj-factors and the magnetic dipole hyperfine constant. Inasmuch as the transitions from the ground state to the 4f and 5f levels in addition to the 6p and 7p levels are forbidden by electric dipole selection rules, we computed all the 5p55d–5p5nf (4 ≤ n ≤ 5), 5p55d–5p5np (6 ≤ n ≤ 7), 5p56s–5p5np (6 ≤ n ≤ 7), 5p57s–5p56p, 5p56d–5p5nf (4 ≤ n ≤ 5), 5p56d–5p5np (6 ≤ n ≤ 7), 5p57s–5p57p and 5p58s–5p5np (6 ≤ n ≤ 7) transition arrays. The present accurate values of spectral lines are obtained by using the well-established multiconfiguration Dirac-Hartree-Fock (MCDHF) method in conjunction with the relativistic configuration interaction (RCI) calculations. The RCI calculations encompass further electron correlation effects. These effects include static electron-valence and core-valence correlation and core polarizations effects, the Breit and quantum electrodynamics (QED) corrections in addition to the effect of nuclear charge distribution. To provide a context for information in the accuracy associated with these values, a detailed comparison of our data with other experimental and theoretical data available in the database is made. On the whole, a good agreement has generally been observed for most of the spectral lines. These newcomers to the area of database with insights into nuclear fusion research, as they may provide diagnostic information on magnetically confined plasmas, they could be a reference point for the identification and de-blending of new spectral lines provided by astrophysics observations and space research.

The pure rotational spectrum of 15ND2 observed by millimetre and submillimetre-wave spectroscopy.

The pure rotational spectrum of the amidogen radical 15ND2 has been observed between 264 and 1051 GHz with a source-modulation millimetre- and submillimetre-wave spectrometer. A total of 346 transitions were identified, although not all of them were resolved, because of the complexity of the fine and hyperfine structures. The set of spectroscopic parameters determined from the analysis of the spectrum refers to rotational, centrifugal distortion and electron spin-rotation interaction terms. Moreover, the hyperfine constants relative to the electronic spin-nuclear spin interaction for both deuterium and nitrogen nuclei and to the nuclear rotation–nuclear spin interaction for nitrogen were also successfully fitted. This work provides the first laboratory observation and spectroscopic characterization of the fully substituted isotopologue of the astrophysically important species NH2.

Automated assignment of rotational spectra using artificial neural networks.

A typical broadband rotational spectrum may contain several thousand observable transitions, spanning many species. While these spectra often encode troves of chemical information, identifying and assigning the individual spectra can be challenging. Traditional approaches typically involve visually identifying a pattern. A more modern approach is to apply an automated fitting routine. In this approach, combinations of 3 transitions are searched by trial and error, to fit the A, B, and C rotational constants in a Watson-type Hamiltonian. In this work, we develop an alternative approach-to utilize machine learning to train a computer to recognize the patterns inherent in rotational spectra. Broadband high-resolution rotational spectra are perhaps uniquely suited for pattern recognition, assignment, and species identification using machine learning. Repeating patterns of transition frequencies and intensities are now routinely recorded in broadband chirped-pulse Fourier transform microwave experiments in which both the number of resolution elements and the dynamic range surpass 104. At the same time, these high-resolution spectra are extremely sensitive to molecular geometry with each polar species having a unique rotational spectrum. Here we train the feed forward neural network on thousands of rotational spectra that we calculate, using the rules of quantum mechanics, from randomly generated sets of rotational constants and other Hamiltonian parameters. Reasonable physical constraints are applied to these parameter sets, yet they need not belong to existing species. A trained neural network presented with a spectrum identifies its type (e.g., linear molecule, symmetric top, or asymmetric top) and infers the corresponding Hamiltonian parameters (rotational constants, distortion, and hyperfine constants). The classification and prediction times, about 160 µs and 50 µs, respectively, seem independent of the spectral complexity or the number of molecular parameters. We describe how the network works, provide benchmarking results, and discuss future directions.

Testing Quantum Electrodynamics in the Lowest Singlet State of Neutral Beryllium-9.

We report spectroscopic results on the 2s2p^{1}P_{1} state in neutral atomic beryllium-9. The absolute frequency for the center of gravity is determined to be 42 565.4501(13) cm^{-1}, a factor of 130 more precise than the previous experimental measurement. The result is in agreement with and a factor of 8 more precise than the current best theoretical estimate of 42 565.441(11) cm^{-1}, which was calculated including the effects of quantum electrodynamics. Because of the large natural linewidth of the transition, the hyperfine constants were not able to be extracted to high precision.

Characterization of Cu2+ Impurity Ion in K₂SnCl6:Cu Single Crystal

K₂SnClSUB6/SUB single crystals doped with Cu were grown by the evaporation of saturated solution. The electron magnetic resonance (EMR) of the CuSUP2+/SUP ion in the crystal has been investigated by using an X-band spectrometer. The rotation pattern in the crystallographic plane together with spin Hamiltonian parameters of CuSUP2+/SUP ion in K₂SnClSUB6/SUB:Cu single crystal shows that the local site symmetry of the CuSUP2+/SUP ion is cubic at room temperature. The calculated spectroscopic splitting factor g of CuSUP2+/SUP impurity ion is 2.1908(±0.0007). The hyperfine constants of CuSUP2+/SUP impurity ion due to the SUP63/SUPCu and 65Cu isotopes in K₂SnClSUB6/SUB:Cu crystal are 0.83(±0.01)×10SUP−4/SUP cmSUP−1/SUP and 0.89(±0.01)×10SUP−4/SUP cmd, respectively. It turns out that the CuSUP2+/SUP ion substitutes for the KSUP+/SUP ion without any nearby charge compensation.

Nuclear spin noise in the central spin model

We study theoretically the spin fluctuations of nuclei in quantum dots. We employ the central spin model which accounts for the hyperfine interaction of the nuclei with the electron spin. We present an analytical solution in the frame of the box model approximation where all hyperfine coupling constants are assumed to be equal. These results are in good agreement with numerical simulations. We demonstrate that in rather high magnetic field the nuclear spin noise spectra has a two-peak structure centered at the nuclear Zeeman frequency with the shape of the spectrum controlled by the distribution of the hyperfine constants.

Electron-nuclear coherent spin oscillations probed by spin-dependent recombination

We demonstrate the detection of coherent electron-nuclear spin oscillations related to the hyperfine interaction and revealed by the band-to-band photoluminescence (PL) in zero external magnetic field. On the base of a pump-probe PL experiment we measure, directly in the temporal domain, the hyperfine constant of an electron coupled to a gallium defect in GaAsN by tracing the dynamical behavior of the conduction electron spin-dependent recombination to the defect site. The hyperfine constants and the relative abundance of the nuclei isotopes involved can be determined without the need of electron spin resonance technique and in the absence of any magnetic field. Information on the nuclear and electron spin relaxation damping parameters can also be estimated from the oscillations damping and the long delay behavior.

Substitutional nitrogen in diamond: A quantum mechanical investigation of the electronic and spectroscopic properties

This paper reports the fully-relaxed lattice and electronic structures, vibrational spectra, and hyperfine coupling constants of the substitutional Ns defect in diamond, derived from B3LYP calculations constructed from all-electron Gaussian basis sets and based on periodic supercells. Mulliken analyses of the charge and spin distributions indicate that the defect comprises a single unpaired electron distributed very largely over both the negatively-charged substituted site and one of the four nearest-neighbour carbon sites, which relaxes away from the impurity. This leads to a local C3v symmetry, with the nitrogen ‘lone pair’ lying along the C3 axis and pointed towards the ‘dangling’ bond of the shifted carbon neighbour. The calculated band gap is 5.85 eV, within which a singly-occupied, majority spin donor band is found ∼2.9 eV above the valence band, and an unoccupied, minority spin acceptor band ∼0.9 eV below the conduction band. Atom-projected densities of states of the donor and acceptor levels show that, contrary to a widespread description, ∼30% only of the donor band derives from nitrogen states per se, with the majority weight corresponding to states associated with the shifted carbon atom. The defect formation energy is estimated to be ∼3.6 eV. The calculated IR spectrum of the impurity centre shows several features between 800 and 1400 cm−1, all of which are absent in the perfect crystal, for symmetry reasons. These show substantial agreement with recent experimental observations. The calculated hyperfine constants related to the coupling of the unpaired electron spin to the N and C nuclei, for which the Fermi contact terms vary from over 200 MHz to less than 3 MHz, are generally in good agreement with the largest experimental values, both in terms of absolute magnitudes and site assignments. The agreement is less good for the smallest two values, for which the experimental assignments are less certain. The results lend support to previous suggestions that some of the weaker lines in the observed spectra, notably those below ∼7 MHz, which are difficult to assign unambiguously, might result from the overlap of lines from different sites.

Theoretical hyperfine structures of F19 i and O17 i

Multiconfiguration Hartree-Fock (MCHF) and multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations are performed for the $2p^{5}~^{2}P^{o}$, $2p^4(^{3}P)3s~^{4}P$, $2p^4(^{3}P)3s~^{2}P$ and $2p^4(^{3}P)3p~^{4}S^o$ states of $^{19}$F~I to determine their hyperfine constants. Several computing strategies are considered to investigate electron correlation and relativistic effects. High-order correlation contributions are included in MCHF calculations based on single and double multireference (SD-MR) expansions. The largest components of the single reference MCHF wave functions are selected to define the MR sets. In this scheme, relativistic corrections are evaluated in the Breit-Pauli approximation. A similar strategy is used for the calculation of MCDHF relativistic wave functions and hyperfine parameters. While correlation and relativistic corrections are found to be rather small for the ground state, we highlight large relativistic effects on the hyperfine constant $A_{3/2}$ of $2p^4(^{3}P)3p~^{4}S^o$ and, to a lesser extent, on $A_{1/2}$ of $2p^4(^{3}P)3s~^{4}P$. As expected for such a light system, electron correlation effects dominate over relativity in the calculation of the hyperfine interaction of all other levels considered. We also revisit the hyperfine constants of $2p^3(^{4}S)3s~^{5}S^{o}$ and $2p^3(^{4}S)3p~^{5}P$ in $^{17}$O using similar strategies. The results are found to be in excellent agreement with experiment.

Extensive and accurate relativistic calculations of atomic data on the 83Kr I spectrum

We provide an extensive, accurate and complete new spectroscopic data set for many levels belonging to the intermediate perturbing Rydberg series ns[K]J (5 ≤ n ≤ 8), nd[K]J (4 ≤ n ≤ 7) and the autoionizing Rydberg series np[K]J (5 ≤ n ≤ 7) and nf[K]J (4 ≤ n ≤ 5) relative to the ground state 4p6 1S0 for neutral krypton-83 isotope. The data set is composed of the energy levels, the oscillator strengths the radiative transition rates the Landé g-factors, the magnetic dipole and electric quadrupole hyperfine constants. The values of these spectroscopic parameters are calculated in the multiconfiguration Dirac-Hartree–Fock (MCDHF) framework. The calculations are carried out in the active space where the electron correlation effects, contributions from relativistic configuration interaction (RCI), the quantum electrodynamics (QED) effects with transverse photon Breit interaction and vacuum photon polarization, specific mass shift and self-energy corrections are included. In addition, we provide the oscillator strengths and transition rates in Coulomb and Babushkin gauges for the 4p5(2P)4d–4p5(2P)5p, 4p5(2P)5s–4p5(2P)5p, 4p5(2P)6s–4p5(2P)5p, 4p5(2P)4d–4p5(2P)44f, 4p5(2P)5d–4p5(2P)4f, 4p5(2P)5d–4p5(2P)6p, 4p5(2P)7s–4p5(2P)6p, 4p5(2P)4d–4p5(2P)5f, 4p5(2P)5d–4p5(2P)5f, 4p5(2P)6d–4p5(2P)5f, 4p5(2P)7p–4p5(2P)6d and 4p5(2P)8s–4p5(2P)7p transition arrays. Extensive comparisons with other experimental and theoretical data from the reference databases are carried out in order to judge the reliability of our data. These comparisons indicate that our results are accurate. The present spectroscopic data may be useful for line identification in observed spectra as well as modelling and diagnostics of astrophysical and fusion plasmas.

Revised energy levels of singly ionized lanthanum

Based on the experimental wavenumbers of 344 spectral lines from calibrated Fourier transform (FT) spectra as well as wavenumbers of 81 lines from the wavelength tables from literature, the energy of 115 fine structure levels of singly ionized lanthanum has been revised by weighted global fits. The classifications of the lines are provided by numerous previous investigations of lanthanum by different spectroscopic methods and authors. For the high accurate determination of the center of gravity wavenumbers from the experimental spectrum, the hyperfine constants of the involved levels have been taken into account, if possible. For the 94 levels with known hyperfine constants the accuracy of energy values is better than 0.01 cm−1. For 34 levels the magnetic dipole hyperfine constants A have been determined from FT spectra as part of this work. For four of these 34 levels even electric quadrupole hyperfine constants B could be estimated. For levels, which have experimentally unknown hyperfine constants and which are connected only by lines not found in the FT spectra but taken from literature, the uncertainties of energy values are about a factor of 10 higher. A list of all revised level energies together with a compilation of hyperfine structure data is given as well as a list of all lines used.

Characterization of free radicals in clathrate hydrates of pyrrole, thiophene, and isoxazole by muon spin spectroscopy

Gas hydrates have long been of interest to the petrochemical industry, but there has been growing interest in potential applications for carbon dioxide sequestration and hydrogen storage. This has prompted many fundamental studies of structure and host–guest interactions, but there has been relatively little investigation of chemical reactions of the guest molecules. In previous work, we have shown that it is possible to use muon spin spectroscopy to characterize H atom like muonium and muoniated free radicals formed in clathrate hydrates. Muonium (Mu) forms in clathrate hydrates of cyclopentane and tetrahydrofuran, whereas furan and its dihydro derivatives form radicals. The current work extends studies to clathrates hydrates of other five-membered heterocycles: thiophene, pyrrole, and isoxazole. All form structure II hydrates. In addition to the clathrates, pure liquid samples of the heterocycles were studied to aid in the assignment of radical signals and for comparison with the enclathrated radicals. Similar to furan, two distinct radicals are formed when Mu reacts with thiophene and pyrrole. However, only one muoniated radical was detected from isoxazole. Muon, proton, and nitrogen hyperfine constants were determined and compared with values predicted by DFT calculations to aid the structure assignments. The results show that Mu adds preferentially to the carbon adjacent to the heteroatom in thiophene and pyrrole and to the carbon adjacent to oxygen in isoxazole. The same radicals are formed in clathrates, but the spectra have broader signals, suggesting slower tumbling. Furthermore, additional signals in the avoided level-crossing spectra indicate anisotropy consistent with restricted motion of the radicals in the clathrate cages.

High-resolution two-photon spectroscopy of a 5p56p←5p6 transition of xenon

We report high-resolution Doppler-free two-photon excitation spectroscopy of Xe from the ground state to the $5{p}^{5}(^{2}P_{3/2})6p\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}^{2}[3/2]_{2}$ electronic excited state. This is a first step to developing a comagnetometer using polarized $^{129}\mathrm{Xe}$ atoms for planned neutron electric dipole moment measurements at TRIUMF. Narrow linewidth radiation at 252.5 nm produced by a continuous wave laser was built up in an optical cavity to excite the two-photon transition, and the near-infrared emission from the $5{p}^{5}6p$ excited state to the $5{p}^{5}6s$ intermediate electronic state was used to detect the two-photon transition. Hyperfine constants and isotope shift parameters were evaluated and compared with previously reported values. In addition, the detected photon count rate was estimated from the observed intensities.

Aggregate frequency width, nuclear hyperfine coupling and Jahn–Teller effect of Cu2+ impurity ion ESR in SrLaAlO4 dielectric resonator at 20 millikelvin

The impurity paramagnetic ion, substitutes Al in the single crystal lattice, this results in a elongated octahedron, and the resulting measured g-factors satisfy four-fold axes variation condition. The aggregate frequency width of the electron spin resonance with the required minimum level of impurity concentration has been evaluated in this single crystal at 20 millikelvin. Measured parallel hyperfine constants, , were determined to be and at for the nuclear magnetic quantum number , and respectively. The anisotropy of the hyperfine structure reveals the characteristics of the static Jahn–Teller effect. The second-order-anisotropy term, , is significant and cannot be disregarded, with the local strain dominating over the observed Zeeman-anisotropy-energy difference. The Bohr electron magneton, , (within so-called experimental error) has been found using the measured spin-Hamiltonian parameters. Measured nuclear dipolar hyperfine structure parameter shows that the mean inverse third power of the electron distance from the nucleus is a.u. for ion in the substituted ion site assuming nuclear electric quadruple moment barn.

Examining transition metal hydrosulfides: The pure rotational spectrum of ZnSH (X̃2A').

The pure rotational spectrum of the ZnSH (X̃2A') radical has been measured using millimeter-wave direct absorption and Fourier transform microwave (FTMW) methods across the frequency range 18-468 GHz. This work is the first gas-phase detection of ZnSH by any spectroscopic technique. Spectra of the 66ZnSH, 68ZnSH, and 64ZnSD isotopologues were also recorded. In the mm-wave study, ZnSH was synthesized in a DC discharge by the reaction of zinc vapor, generated by a Broida-type oven, with H2S; for FTMW measurements, the radical was made in a supersonic jet expansion by the same reactants but utilizing a discharge-assisted laser ablation source. Between 7 and 9 rotational transitions were recorded for each isotopologue. Asymmetry components with Ka = 0 through 6 were typically measured in the mm-wave region, each split into spin-rotation doublets. In the FTMW spectra, hyperfine interactions were also resolved, arising from the hydrogen or deuterium nuclear spins of I = 1/2 or I = 1, respectively. The data were analyzed using an asymmetric top Hamiltonian, and rotational, spin-rotation, and magnetic hyperfine parameters were determined for ZnSH, as well as the quadrupole coupling constant for ZnSD. The observed spectra clearly indicate that ZnSH has a bent geometry. The rm(1) structure was determined to be rZn-S = 2.213(5) Å, rS-H = 1.351(3) Å, and θZn-S-H = 90.6(1)°, suggesting that the bonding occurs primarily through sulfur p orbitals, analogous to H2S. The hyperfine constants indicate that the unpaired electron in ZnSH primarily resides on the zinc nucleus.