由基样条构造有限基集计算的超精细结构常数(英文)

多体微扰论有效算符方法应用于超精细结构的计算 .由HF波函数计算零阶超精细常数 .使用基样条构造了薛定谔方程的有限基集 .使用这些有限基集计算了原子实极化和关联 ,以及 7Li,2 3 Na ,3 9K和4 3 Ca离子的s1/ 2 ,p1/ 2 和p3 / 2 态的超精细结构常数和4 3 Ca离子的d3 / 2和d5/ 2 态的超精细常数 . The effective-operator form of many-body theory is applied to the calculation of hyperfine structure. The zeroth order hyperfine constants are evaluated with Hartree-Fock wavefunction. Τhe finite basis sets of Schrdinger s equation are constructed by using B-splines. With the finite basis sets, we have calculated the core polarization, and the correlation diagrams. The hyperfine constants of the s 1/2, p 1/2and p 3/2 states of 7Li, 23Na, 39K, 43Ca + as well as the d 3/2...     

Hyperfine Constants for Low-Lying States in ^137Ba^＋

Relativistic many-body perturbation calculation is applied to calculate the hyperfine constants for the lowlying states 6S1/2, 6P1/2, 6P3/2, 5D3/2, and 5D5/2 in the alkaline earth ion ^137Ba^＋. The zeroth-order hyperfine constants are calculated with Dirac-Fock wave functions, and the finite basis sets of the Dirac-Fock equation are constructed by B splines. With the finite basis sets, the core polarization and the correlation effect are calculated. The final results for magnetic dipole hyperfine a constants are obtained.     

Calculation of the hyperfine structure constants in 85Rb and 133Cs

For heavy atoms or ions, such as, Rb and Cs et al., relativistic effect must be considered in the calculation. In this paper, the relativistic many-body perturbation theory is used to solve the Dirac equation. And the zeroth-order hyperfine constants are evaluated with Dirac-Fock wave function. The finite basis sets of dirac equation are constructed by B-splines. With the finite basis sets the core polarization and the correlation diagrams are calculated. The hyperfine structure constants of the 5S1/2 and 6S1/2 states of 85Rb as well as the 6S1/2 and 7S1/2 states of 133Cs are evaluated.     

Unrestricted hartree-fock cluster analysis of F and F A centres in some alkali halides

The optical absorption energies and nearest-neighbour ground state hyperfine interaction constants are evaluated for F centres in lithium and potassium halides, and for FA(Li) centres in KC1 and KBr. For these defects, the electron-ion interaction includes self-consistent unrestricted Hartree-Fock treatment of nearest-neighbour ions, in terms of Gaussian-localized atomic orbital basis functions. The results, with the exception of FA-centre hyperfine constants, are qualitatively correct.     

Relativistic coupled cluster method

Relativistic coupled cluster method (CCM) is applied to compute the low lying excited and ion states of strontium and ytterbium atom. The resulting excitation and ionization energies are in excellent agreement with experimental data and with other correlated calculations. The nuclear magnetic dipole hyperfine constants (A) and electric quadrupole hyperfine constants (B) of excited states are also evaluated and are in accord with experiment. We further address the basis set dependency of the computed properties.     

Influence of the basis set and convergence in ab-initio valence-bond calculations

Extended and minimal basis set ab-initio valence-bond (VB) calculations have been performed for the following molecules: LiH, CH, ¹CH₂, ³CH₂, CH₃, NH₃ and H₂O. The influence of the choice of the basis sets and of the structures included on the values of a few observables, including energy, geometry, hyperfine coupling constants and dipole moment, has been studied.     

Hyperfine structure in internal rotor molecules

The theory of magnetic hyperfine interactions in internal rotor molecules with one internal degree of freedom has been developed as basis for the interpretation of hyperfine structure in the microwave spectra of these molecules. It has been shown that the internal rotation modifies the familiar nuclear spin-spin and spin-rotation interactions. Explicit expressions for the hyperfine energy matrix elements and coupling constants are derived for the methanol molecule.     

B splines有限基矢集用于多体微扰计算

讨论了用B splines构造有限正交基矢集的方法,并将这种基矢用于超精细相互作用的多体微扰计算,得到了与实验一致的结果。 关键词：     

Elektronen-Kern-Doppelresonanz-Untersuchung vonU 2-Zentren in Kaliumchlorid

U ₂-centers in alkali halides are neutral hydrogen atoms in interstitial lattice sites, as has been shown by EPR measurements. The hyperfine interactions with the proton and with the four nearest halogen nuclei are resolved in the EPR spectrum. In order to resolve hyperfine interactions with further nuclei of the surrounding lattice ENDOR measurements have been performed onU ₂-centers in KCl at 77 °K. The analysis of the ENDOR spectra gave precise values for the hyperfine and quadrupole interaction constants of the nearest neighbour chlorine and potassium nuclei. The isotropic hyperfine constant of the chlorine neighbours is 24 times larger than that of the potassium neighbours although both nuclei are on equivalent first shell lattice positions. The hyperfine interactions of second shell potassium nuclei [(1/2, 1/2, 3/2)-position] show an unexpectedly large isotropic hyperfine constant. One expects a pure magnetic dipole-dipole interaction for the outer shell nuclei because of the concentrated hydrogen wave function. Two further chlorine shells could be approximately analysed. A theoretical estimate of the hyperfine and quadrupole interaction constants was made by orthogonalizing the 1s hydrogen wave function to the cores of the surrounding ions. If one takes into account the mutual overlap of neighbouring potassium and chlorine ions, one gets the right order of magnitude of the measured constants and a value of 10.4∶1 for the ratio of the isotropic hyperfine constants of the first shell chlorine and potassium nuclei. The relatively large isotropic constant of the second shell potassium nuclei can also be explained on this basis.     

High resolution measurements of the hyperfine structure of atomic Lanthanum for energetically low lying levels of odd parity

Doppler-reduced saturation absorption spectroscopy is applied to study the hyperfine structure of excited levels of Lanthanum. 16 transitions in the near infrared wavelength range are investigated. Precise values for the magnetic dipole hyperfine structure constants A as well as for the electric quadrupole hyperfine structure constants B of the isotope ¹³⁹La are determined for 14 levels of odd parity and nine levels of even parity. For levels of even parity a good agreement is found with values from previous measurements using sub-Doppler methods. For levels of odd parity previously determined values are improved and for two levels new values of the hyperfine structure constants are reported.     

Rotational spectra of isotopic species of silyl fluoride. Part I: Lamb-dip measurements and quantum-chemical calculations

The Lamb-dip technique has been employed for recording the rotational spectra of three isotopic species of silyl fluoride, namely ²⁸SiH₃F, ²⁹SiH₃F, and ³⁰SiH₃F, in order to improve the knowledge of their spectroscopic parameters as well as to try to resolve their hyperfine structure. High-level quantum-chemical computations using state-of-the-art coupled-cluster techniques together with core-polarized correlation-consistent basis sets have been employed to provide reliable reference values for the hyperfine parameters involved and have been used to guide the experimental investigation. Analysis of the experimental spectra allowed to improve the accuracy of the known spectroscopic parameters as well as to determine for the first time sextic and octic centrifugal-distortion constants.     

Resonance Energies,Absorption Oscillator Strengths and Ionization Potentials for the Element Hassium （Z = 108）

On the basis of successfully predicting low-lying energy levels for the element fermium （Z = 100）, we calculate the resonance energies, absorption oscillator strengths and the first ionization potential of the element hassium （Z = 108） by taking important relativistic and improved electron correlation effects into account using the multiconfiguration Dirac Fock method. These calculations are carried out with the aim of assisting experimental investigations of hassium.     

Extraction of hyperfine anomalies without precise values of the nuclear magnetic dipole moment

A new method for extracting the hyperfine anomaly from experimental hyperfine structure constants is suggested. Instead of independent high-precision measurements of the nuclear magnetic dipole moment, precise measurements of magnetic dipole hyperfine interaction constants for two atomic states and a theoretical analysis can be used. This can lead to determination of hyperfine anomaly for radioactive isotopes where the nuclear magnetic dipole moment is not known with high accuracy. Received: 17 February 1998     

MCHF+BP Approaches of Hyperfine Interaction Constants in 45SII

Multi-configuration Hartree-Fock and configuration interaction calculations of hyperfine structure constants for 3d^{2 3}P states of ScII are reported. It is very important to consider core polarization (especially spin polarization) and core-core correlation as well as valence correlation for accurate calculation of hyperfine constants. The relativistic correction (through Breit-Pauli approximation) as well as finite-nuclear-mass and fnite-nuclear-size-corrected values of the hyperfine constants for ScII are in good agreement with the most accurate experimental values and better than other ab initio theoretical results.     

Anisotropic hyperfine structure in the EPR spectrum of impurity ions in single crystals

Expressions are obtained for the hyperfine splitting in EPR spectra of impurity ions with electron spin 1/2 and arbitrary nuclear spin for arbitrary anisotropy of the g-factor and hyperfine structure constants. These results generalize the previously obtained results of Weil for the case of weakly anisotropic g-factors and hyperfine structure constants. Fiz. Tverd. Tela (St. Petersburg) 41, 1026–1027 (June 1999)     

Comparative studies of the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of 25Mg+

We have employed the relativistic coupled cluster theory to calculate the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of singly ionized magnesium. Comparison with experimental and the other theoretical results are done and predictions are also made for a few low lying excited states which could be of interest. We have made comparative studies of the important many body effects contributing to the hyperfine constants for the different states of the ion.     

电子关联对类铍离子1s~22s2p~3P_(0,1)能级的超精细结构常数的影响

基于MCDF方法系统地计算了Z=20~83范围内24个类铍离子的1s22s2p3P0,1态的精细结构,得到了与其它理论和实验符合很好的结果.在此基础上,进一步计算了超精细结构对角及非对角常数,并分析了不同电子关联效应和Breit相互作用对它们的影响.     

Submillimeter-wave spectroscopy of VN (XΔr) and VO (XΣ): A study of the hyperfine interactions

The pure rotational spectra of VN (X³Δ_r) and VO (X⁴Σ⁻) have been recorded in the frequency range 290-520 GHz using direct absorption spectroscopy. These radicals were synthesized in the gas-phase from the reaction of VCl₄ with either N₂ or H₂O in an AC discharge. Seven rotational transitions were recorded for each molecule; in both sets of spectra, fine and hyperfine structures were resolved. The data sets for VN and VO were fit with Hund’s case (a) and case (b) Hamiltonians, respectively, and rotational, fine structure, and hyperfine constants determined. For VN, however, an additional hyperfine parameter, Δa, was necessary for the analysis of the Ω = 2 sublevel to account for perturbations from a nearby ¹Δ state, in addition to the usual Frosch and Foley constants. Determination of Δa suggests that the ¹Δ state lies ∼3000 cm⁻¹ above the ground state. In VO, the hyperfine structure in the F₂ and F₃ components was found to become heavily mixed due to an avoided crossing, predicted by previous optical studies to be near the N = 15 level. The hyperfine constants established for these two molecules are consistent with the proposed σ¹δ¹ and σ¹δ² electron configurations.     

铥原子激发能级超精细结构常数的测定

用铥空心阴极灯,采用光电流光谱技术测得铥原子21条一级跃迁谱线,确定了相应跃迁上能级的超精细结构常数,其中7个能级的参数为首次发表,运用同一空心阴极灯,采用双色双光子级联共振技术,由荧光法首次测得4个第二激发能级的超精细结构常数.