Hyperfine Structure Constants Research Articles

An investigation of local structures for 3d3, 3d5 and 3d7 ions doing in the layered LiCoO2 cathode materials

Doping transition metal ions in LiCoO2 batteries has been proved an efficient method to improve the electrochemical properties in experiment, which is deeply related with the distorted local structure of impurities ions. According to the observed EPR spectra, the distorted local structures for 3d3 (Mn4+), 3d5 (Fe3+) and 3d7 (Ni3+) ions in LiCoO2 batteries are theoretically studied based on the perturbation calculations of Spin Hamilton Parameters (g factors, hyperfine structure constants A and Zero-field splittings parameters D and E). By considering the Jahn-Teller effect and mismatch radius of above transition metal ions (TMs), the formed [MnO6]8-, [FeO6]9- and [NiO6]9- clusters in LiCoO2 exhibit various distorted symmetries compared with experimental single one, characterized by trigonal distortion parameter Δθ as well as rhombic distortion parameters ΔZ and Δϕ in the 3d3 center and the 3d5 center and tetragonal distortion parameter ΔZ in the 3d7 center. In addition, compared with asymmetrical signal of EPR spectra at 30K, the role of relatively high temperature for 100K is investigated by dynamic Jahn-Teller, making the isotropic EPR signal and regular octahedron for Ni3+ center. Comparing with the obtained structure properties of isolate-doped transition metal ion, the co-doped Mg in LiCoO2 makes the further elongated distortion of local structure. Based on the well fitted EPR parameters and obtained local environment of doped transition metal ions, the inactive of electrochemical properties of Mn4+ can be attribute to the largest crystal field (Dq) and the smallest difference with host Co3+ site. Therefore, a comprehensively study of the local structure may be helpful to understand and predict the electrochemical behaviors of batteries.

Studies on the local structure and spin Hamiltonian parameters for V4+ in Na2 O-PbO-Bi2 O3 -SiO2 glass ceramics.

The local structure, d-d transition band, and spin Hamiltonian parameters (SHPs) are theoretically studied for the V4+ probe in Na2 O-PbO-Bi2 O3 -SiO2 (NPBS) glass ceramics containing V2 O5 dopant with various concentration x (0 ≤ x ≤ 5 mol%) by using the perturbation formulas of the SHPs for tetragonally compressed octahedral 3d1 clusters. The first decreasing (or increasing) and then increasing (or decreasing) d-d transition band (= 10 Dq ) and hyperfine structure constants A// and A⊥ (or g factors g// and g⊥ ) with x can be suitably simulated with the similarly varying Fourier type concentration functions of cubic field parameter Dq , covalence factor N, core polarization constant κ, and reduction factor H (or relative tetragonal compression ratio ρ), with the minima (or maxima) at the middle concentration x = 3 mol%, respectively. The above concentration variations of SHPs and the related quantities may originate from the modifications of local crystal field strength, tetragonal compression, and electron cloud distribution near the impurity V4+ with x, corresponding to the highest [V4+ ]/[V5+ ] ratio at 3 mol%. Present studies would be helpful to explore novel sodium lead bismuth silicate glass ceramics by modifying the concentration of V2 O5 dopant.

Relativistic configuration-interaction and many-body-perturbation-theory calculations of U i hyperfine constants

Neutral uranium (U I) is a very difficult atom for theoretical calculations due to a large number of valence electrons, six, strong valence-valence and valence-core correlations, high density of states, and relativistic effects. Configuration-interaction many-body perturbation theory (CI-MBPT) can treat efficiently valence-core correlations and relativistic effects, but because the formalism was developed for Dirac-Hartree-Fock (DHF) starting potential that does not contain valence electrons, quite large CI space is needed to compensate for +6 charge of such a potential. Much more efficient is relativistic configuration-interaction (RCI) approach which uses relatively accurate starting DHF potential that includes some valence electrons to make the valence electron Hamiltonian diagonally dominated for some states. Here we report calculations of U I hyperfine constants of several low-energy states using the RCI method with the starting potential that includes four f valence electrons. With this starting potential, it is possible to use the single-configuration approximation or small basis sets to obtain quite accurate results for hyperfine structure constants. In fact, by scaling nuclear magnetic moment, the agreement for 5 levels was within 5\%, and a new magnetic moment can be recommended 0.43(2). The method can be further developed to include more extensive data sets to improve accuracy and can be applied to other atoms and for calculations of other properties, for example, relevant to fundamental symmetry tests.

Calculation of the Hyperfine Magnetic Anomaly in Many-Electron Atoms

The precision measurements of the ratio of hyperfine structure constants for $s_{1/2}$ and $p_{1/2}$ states allow us to estimate the difference between hyperfine magnetic anomalies for these levels. We calculate the atomic factor in order to recover the absolute values of the hyperfine magnetic anomalies from their difference. Taking into account the hyperfine anomaly correction allows one to increase the accuracy of determining the g-factors of short-lived isotopes by more than an order of magnitude.

New energy levels of La I deduced from the investigation of red spectral lines

By means of laser spectroscopy and optogalvanic detection, we searched for unknown spectral lines of atomic lanthanum (La I) in the red region of the visible spectrum (6900–6200 Å). Most of the discovered lines could be interpreted as transitions between known energy levels due to wavelength and observed hyperfine structure pattern. For lines which we could not classify we searched for laser-induced fluorescence in order to identify at least one level involved in the transition. In this way we discovered 25 energy levels of La I having even parity. For two levels we could improve the accuracy of energy and hyperfine structure constants. These 27 levels classify 213 spectral lines.

Nuclear Magnetic Moments of Francium-207-213 from Precision Hyperfine Comparisons.

We report a fourfold improvement in the determination of nuclear magnetic moments for neutron-deficient francium isotopes 207-213, reducing the uncertainties from 2% for most isotopes to 0.5%. These are found by comparing our high-precision calculations of hyperfine structure constants for the ground states with experimental values. In particular, we show the importance of a careful modeling of the Bohr-Weisskopf effect, which arises due to the finite nuclear magnetization distribution. This effect is particularly large in Fr and until now has not been modeled with sufficiently high accuracy. An improved understanding of the nuclear magnetic moments and Bohr-Weisskopf effect are crucial for benchmarking the atomic theory required in precision tests of the standard model, in particular atomic parity violation studies, that are underway in francium.

Electron paramagnetic resonance study of the paramagnetic center in gamma-irradiated tetrahydrophthalic anhydride single crystal

Electron Paramagnetic Resonance (EPR) analysis of gamma-irradiated tetrahydrophthalic anhydride (C8H8O3) single crystals was performed at 120 K. The single crystals were exposed to 60Co-gamma source at room temperature. The EPR spectra of gamma-irradiated single crystals of tetrahydrophthalic anhydride (THPA) were recorded at 10-degree intervals for different orientations of crystals in a magnetic field. Detailed examination of THPA single crystals by EPR spectroscopy method showed the presence of two carbon-centered THPA anion radicals. Both radicals were determined to have the same structure. The anion radicals observed in gamma-irradiated THPA single crystal were created by the scission of the carbon–oxygen double bond. The g values of the radiation damage centers observed in the THPA single crystal and the hyperfine structure constants of the free electron with nearby protons were obtained. Highlights Single crystals of tetrahydrophthalic anhydride were exposed to gamma radiation. Radiation damage centers in single crystals of tetrahydrophthalic anhydride were determined by EPR spectroscopy method. The presence of two anion radicals in single crystals of tetrahydrophthalic anhydride was determined. The formation mechanism of the paramagnetic centers in the tetrahydrophthalic anhydride is similar to that of succinic anhydride.

Studies of the EPR parameters and tetragonal distortion for the Cu2+ center in aluminium oxide

The electronic paramagnetic resonance (EPR) parameters (g factor gi , and hyperfine structure constants Ai , with i = || and ⊥) and tetragonal distortion of the Cu2+ center in Al2O3 are unified interpreted from the perturbation formulas for a 3d9 ion in tetragonally elongated octahedral. In the calculations, the impurity Cu2+ is found to occupy the host trigonally-distorted octahedral Al3+ site with the tetragonal elongation distortion due to the Jahn–Teller effect, despite the original trigonal distortion of the host cation site. The contributions to EPR parameters from both the spin–orbit coupling of the central ion and that of the ligands are taken into account. The defect structure of the Cu2+ center (characterized by the relative tetragonal elongation ratio η ≈ 4.3% along the C 4 axis) was determined from the calculation. Furthermore, the calculated results agree well with the experimental data and need fewer adjustable parameters than the previous studies.

Laser spectroscopy of indium Rydberg atom bunches by electric field ionization

This work reports on the application of a novel electric field-ionization setup for high-resolution laser spectroscopy measurements on bunched fast atomic beams in a collinear geometry. In combination with multi-step resonant excitation to Rydberg states using pulsed lasers, the field ionization technique demonstrates increased sensitivity for isotope separation and measurement of atomic parameters over previous non-resonant laser ionization methods. The setup was tested at the Collinear Resonance Ionization Spectroscopy experiment at ISOLDE-CERN to perform high-resolution measurements of transitions in the indium atom from the text {5s}^2text {5d},^2text {D}_{5/2} and text {5s}^2text {5d},^2text {D}_{3/2} states to text {5s}^2np ^2P and text {5s}^2ntext {f},^2F Rydberg states, up to a principal quantum number of n=72. The extracted Rydberg level energies were used to re-evaluate the ionization potential of the indium atom to be 46,670.107(4),hbox {cm}^{-1}. The nuclear magnetic dipole and nuclear electric quadrupole hyperfine structure constants and level isotope shifts of the text {5s}^2text {5d},^2text {D}_{5/2} and text {5s}^2text {5d},^2text {D}_{3/2} states were determined for ^{113,115}In. The results are compared to calculations using relativistic coupled-cluster theory. A good agreement is found with the ionization potential and isotope shifts, while disagreement of hyperfine structure constants indicates an increased importance of electron correlations in these excited atomic states. With the aim of further increasing the detection sensitivity for measurements on exotic isotopes, a systematic study of the field-ionization arrangement implemented in the work was performed at the same time and an improved design was simulated and is presented. The improved design offers increased background suppression independent of the distance from field ionization to ion detection.

Optical clocks based on the Cf15+ and Cf17+ ions

Recent experimental progress in cooling, trapping, and quantum logic spectroscopy of highly-charged ions (HCIs) made HCIs accessible for high resolution spectroscopy and precision fundamental studies. Based on these achievements, we explore a possibility to develop optical clocks using transitions between the ground and a low-lying excited state in the Cf$^{15+}$ and Cf$^{17+}$ ions. Using a high-accuracy relativistic method of calculation we predicted the wavelengths of clock transitions, calculated relevant atomic properties, and analyzed a number of systematic effects (such as the electric quadrupole-, micromotion-, and quadratic Zeeman shifts of the clock transitions) that affect the accuracy and stability of the optical clocks. We also calculated magnetic dipole hyperfine-structure constants of the clock states and the blackbody radiation shifts of the clock transitions.

Investigation of the Optical Spectra and Spin-Hamiltonian Parameters for Vanadyl in Zinc Phosphate Glass

The optical absorption spectra and spin-Hamiltonian parameters (g factors g||, g⊥, and hyperfine structure constants A||, A⊥ ) of vanadyl in zinc phosphate glass are investigated, using the high-order perturbation formulas for a 3d1 ion in tetragonally compressed octahedra. In the calculations, the required crystal-field parameters are estimated from the superposition model, and the optical absorption bands and spin-Hamiltonian parameters are linked with the tetragonal distortion (characterized by ΔR = R⊥ – R||, where R⊥ and R|| denote the bond lengths perpendicular and parallel to the C4 axis). Based on the calculations, the tetragonal distortion ΔR (≈1.795 A) was obtained, and negative signs of the hyperfine structure constants A|| and A⊥ are suggested.

Hyperfine structure studies of the electronic levels of the manganese atom. II. Odd-parity level system

The hyperfine structure of 15 spectral lines of the manganese atom was investigated with the method of laser induced fluorescence on an atomic beam. Results of these investigations, supplemented by the results obtained in Part I of this work series, yielded the hyperfine structure constants A and B for altogether 38 odd-parity levels. For 11 levels the A and B values are reported for the first time, for another 10 levels new constants B were evaluated, and for the remaining 17 levels the accuracy of the hitherto available literature data was improved; thus the available database of the hyperfine structure constants for the manganese atom was considerably extended. A semi-empirical fit of the fine and the hyperfine structure for the odd-parity level system of the atomic manganese was also performed in the present work; generally a good agreement between the experimental and the calculated values was found.

Relativistic coupled-cluster study of BaF in search of violation

BaF is one of the potential candidates for the experimental search of the electric dipole moment of the electron (eEDM). The NL-eEDM collaboration is building a new experimental set up to measure the eEDM using the BaF molecule (The NL-eEDM collaboration, 2018 Eur. Phys. J. D 72: 197). To analyze the results of such an experiment, one would require the accurate value of the molecular -odd interaction parameters that cannot be measured from any experiment. In this work, we report the precise value of the -odd interaction parameters of the BaF molecule obtained from the four-component relativistic coupled-cluster calculations. We also calculate the hyperfine structure (HFS) constants of the same molecule to assess the reliability of the reported molecular parameters. The calculated HFS constants show good agreement with the available experimental values. Further, the systematic effects of electron-correlation along with the roles of inner-core electrons and the virtual energy functions in the calculation of the studied properties of BaF are investigated.

New energy levels of atomic lanthanum with small total angular momentum quantum number discovered by laser spectroscopic methods in the near IR

Optogalvanic spectroscopy as well as laser-induced fluorescence spectroscopy were applied in order to find new energy levels of atomic lanthanum. A hollow-cathode lamp and a tuneable continuous wave titanium-sapphire laser in the wavelength range from 750 nm to 850 nm were used for the measurements. Three energy levels of even parity with small values of total angular momentum quantum number J were discovered: 38 519.18 cm−1with J=1/2,40 392.80 cm−1with J=3/2,and 42 191.24 cm−1with J=3/2. The existence of these three levels was confirmed by laser excitations of several spectral lines as well as by spectral lines from a Fourier transform spectrum. Magnetic dipole hyperfine structure constants of the three new levels were determined from fits of the experimental spectra of the laser lines.

Investigations of the hyperfine structure and isotope shifts in the even-parity level system of atomic europium

This work presents the measurements of the hyperfine structure constants A and B, as well as the isotope shifts, for 26 electronic levels belonging to the even-parity configurations at the energy range 28000–40000 cm−1 in the europium atom. The measurements were performed with the use of laser spectroscopy with a hollow cathode discharge lamp as the source of the atoms and the detection of laser induced fluorescence. Among the results obtained, 10 levels were measured for the first time, in the case of another 3 levels results somewhat more precise than the earlier published ones were obtained. The A and B hyperfine structure constants’ values were determined on the basis of the measurements on 73 spectral lines located in two wavelength ranges: 480–560 nm and 625–680 nm.

Hyperfine Structure Constants for Levels of 175Lu+

Hyperfine Structure Constants for Levels of ¹⁷⁵Lu⁺

Hyperfine structure studies of the electronic levels of the manganese atom. I. Even-parity level system

In this work the hyperfine structure of 26 even-parity levels of the manganese atom was investigated with the method of laser induced fluorescence on an atomic beam. Altogether 47 spectral lines were examined, with the even-parity levels involved as the lower levels. For three levels both the constants A and B were determined for the first time, for another eight levels new constants B were obtained. The obtained results concerning the even-parity levels contributed to a considerable extension of the available database of the hyperfine structure constants for the atomic manganese. The values obtained were included in a semi-empirical analysis of the fine and the hyperfine structure for the even-parity configurations system, performed also in this work. A good agreement between the experimental and the theoretically predicted hyperfine structure constants was achieved.

Hyperfine Structure Constants on the Relativistic Coupled Cluster Level with Associated Uncertainties.

Accurate predictions of hyperfine structure (HFS) constants are important in many areas of chemistry and physics, from the determination of nuclear electric and magnetic moments to benchmarking of new theoretical methods. We present a detailed investigation of the performance of the relativistic coupled cluster method for calculating HFS constants within the finite-field scheme. The two selected test systems are 133Cs and 137BaF. Special attention has been paid to construct a theoretical uncertainty estimate based on investigations on basis set, electron correlation and relativistic effects. The largest contribution to the uncertainty estimate comes from higher order correlation contributions. Our conservative uncertainty estimate for the calculated HFS constants is ∼5.5%, while the actual deviation of our results from experimental values is <1% in all cases.

Hyperfine anomaly in gold and magnetic moments of Iπ=11/2− gold isomers

Hyperfine-structure constants for the 6s2S1/2 and 6p2P1/2 atomic states of the Iπ=11/2− gold isomers Aum177,191,193,195 have been measured at CERN-ISOLDE, using the in-source laser resonance-ionization spectroscopy technique. From the measured hyperfine constants the differences between hyperfine anomalies for these atomic states have been deduced. These differential hyperfine anomaly values have been used to determine the 6s-state hyperfine anomaly relative to the stable Au197 with advanced atomic calculations. Magnetic dipole moments for the gold isomers in question have been deduced, taking into account the corresponding relative hyperfine-anomaly values. It has been shown that the commonly used prescription for the extraction of the magnetic moment values for the gold isotopes should be reconsidered. The magnetic moments calculated by this prescription have been reevaluated by properly accounting for the hyperfine anomaly, which is as large as 10% for several gold isotopes.

Accurate determination of energy levels, hyperfine structure constants, lifetimes and dipole polarizabilities of triply ionized tin isotopes

We have investigated the energies, magnetic dipole hyperfine structure constants (Ahyf) and electric dipole (E1) matrix elements of a number of low-lying states of triply ionized tin (Sn3+) by employing relativistic coupled-cluster theory. Contributions from the Breit interaction and lower-order quantum electrodynamic (QED) effects in the determination of the above quantities are also given explicitly. These higher-order relativistic effects are found to be important for the accurate evaluation of energies, while only QED contributions are seen to contribute significantly to the determination of Ahyf values. Our theoretical results for the energies are in agreement with one of the measurements but show significant differences for some states with another measurement. Reported Ahyf will be useful in guiding the measurements of hyperfine levels in the stable isotopes of Sn3+. The calculated E1 matrix elements are further used to estimate the oscillator strengths, transition probabilities and dipole polarizabilities (α) of many states. Large discrepancies between the present results and previous calculations of oscillator strengths and transition probabilities are observed among a number of states. The estimated α values will be useful for carrying out high precision measurements using the Sn3+ ion in future experiments.