Study of the energy level structure for ions of the thallium isoelectronic sequence

The structure of the energy level diagram for 30 ions of the thallium isoelectronic sequence is studied on the basis of the relativistic Dirac-Fock self-consistent field method with the configuration interaction taken into account. It is discovered that the ground-state configuration and the lowest term change along the thallium isoelectronic sequence: At the beginning of the sequence, the ground-state configuration is 6s ²6p, and it becomes 6s ²6f beginning from the Cf¹⁷⁺ ion. On the basis of theoretical calculations, the ground-state ionization potentials are determined for each ion. The influence of interaction of the 6s6p ² configuration with the 6s ²6d configuration on the ² D _{3/2, 5/2} levels of the latter was also studied, and values of the fine-structure splitting of the 6s ²6p ² P ⁰ and 6s ²6d ² D levels were determined for the Tl-like ions considered.     

Wavelengths and transition probabilities for the nitrogen isoelectronic series

The energies of transitions of the type 1 s² 2 s² 2 p³-1 s² 2 s 2 p⁴-1 s² 2 p⁵ were computed for isoelectronic sequence of nitrogen. The account was taken of the Hartree-Fock and correlation energies in the first two-three orders of the perturbation theory and the relativistic corrections in terms of Breit operator. The computed values were compared with experimental results for the isoelectronic oxygen series. Sufficiently good agreement of the computed and experimental results for all isoelectronic sequence manifests rather fast convergence in the series of powers of 1/Z. The perturbation theory was employed in computing the transition probabilities of 1 s² 2 s² 2 p³-1 s² 2 s 2 p⁴-1 s² 2 p⁵. The data computed may be used in the identification of the coronal solar spectra and the spectra of high-temperature plasma obtained under the laboratory conditions.To conclude it is our pleasant duty to thank Drs. S. L.Mandel'shtam, L. A.Vainshtein, E. Ya.Kononov and K. N.Koshelev for useful discussions and interest to the present work.     

类锂硅离子能级结构及软X射线激光光谱理论计算

本文采用Hartree-Fock自洽场方法,从理论上计算出类锂硅离子1s~2nl(n=2～7,l=0～5)各能级能量,并给出在极紫外(波长小于400(?))范围内各跃迁谱线的光谱性质、波长、振子强度和跃迁几率.对实验中已实现软X射线激光的跃迁(5d-3p,5f-3d,6d-3p,6f-3d),计算所得的跃迁波长与实验值完全相符.与现有文献的波长比较,相对误差不超过1%.     

Wave functions for two- and three-electron atoms and isoelectronic ions

We have developed simple wave functions for two- and three-electron atoms and ions, which have the correct structure when one of the electrons is far away, or when two of the particles are close to each other. These essentially parameter-free wave functions allow us to deduce fairly accurate values for the energies, , for multipolar polarizabilities of two-electron atoms and ions, and for the coefficients of the asymptotic density. Received: 5 August 1998 / Received in final form: 27 November 1998     

Kinetic and potential energy of isoelectronic atomic ions from density functional theory compared with exact values

The performance of the Fock exchange and the two most common Becke exchange functionals, B88 and B3, in combination with Perdew and Wang's correlation functional (PW91) has been studied for highly charged atomic ions. The study focuses on the accuracy of the components of total energy: kinetic and potential energy. It is found that Becke's exchange functionals introduce a significant error in the kinetic and nuclear attraction energy for most ions studied, and the use of these exchange functionals might lead to inaccurate momentum distributions when their Kohn-Sham orbitals are transformed to momentum space.     

Radiative transition probabilities in ions of the silver isoelectronic sequence

The wave functions of one-electron states above the 4d ¹⁰ core have been calculated within the relativistic perturbation theory with a zero-order model potential. The wavelengths and probabilities of electric dipole transitions in an Ag-like ion have been calculated for the 5s-5p, 5p-5d, 5d-5f, and 4f-5d transitions. The data obtained are compared with the results of calculations by the relativistic Hartree-Fock method and within the relativistic many-body perturbation theory. The theoretical results are compared with experimental data on the lifetimes of energy levels in Ag-like ions.     

Study on the n = 5 complex transitions for ions Nd XIII-Sm XV in Cd I isoelectronic sequence

The energy levels of the n = 5 complex configuration 5s2, 5s5p, 5s5d and 5p2 were computed for Cd I isoelectronic sequence ions from I VI to Sm XV by Hartree-Fock with relativistic corrections (HFR) method. By analyzing the variation of difference deltaE between energy levels calculated by HFR method and the experimental values with Z(c) along this isoelectronic sequence, the authors put forward a new fitting formula for generalized-least-square-fit (LSF) calculation. Using this formula and the FORTRAN programme designed by us, the energy levels of configurations mentioned above were calculated. The unknown energy levels of configuration 5s2 , 5s5p, 5s5d and 5p2 for ions from Nd XIII-Sm XV were predicted by extrapolation (or interpolation). Also, the wavelengths and HFR probabilities of transition 5s2-5s5p, 5s5p-5p2 and 5s5p-5s5d were computed. The calculated energy levels and wavelength results are in good agreement with corresponding experimental data reported in the references.     

Electronic structure patterns of isoelectronic compounds

X-ray photoelectron spectra of the valence levels of AO₄^x? anions (A = P, S, Cl, As, Se), AO₃^x? anions (A = S, Cl, I, Se, Te, Br) and AF₆^x? anions (A = Al, Si, As) have been studied. The spectra are interpreted and the electronic structures are considered for the isoelectronic and isovalent compounds.     

Excited states of Ne isoelectronic ions: SAC-CI study

Excited states of the s, p, and d symmetries up to principal quantum number n = 4 are studied for the first eight members of Ne isoelectronic sequence (Ne to Cl⁷⁺) by the SAC-CI (symmetry-adapted-cluster configuration-interaction) method. The valence STO basis sets of Clementi et al. and the optimized excited STO are used by the STO-6G expansion method. The calculated transition energies agree well with the experimental values wherever available. Received 26 July 2000 and Received in final form 14 September 2000     

Radiative constants in the spectra of ions of the krypton isoelectronic sequence

The probabilities of the 4p ⁶,4p ⁵5p→4p ⁵(4d+5s) radiative transitions and the radiative lifetimes of the 4p ⁵4d,4p ⁵5s, and 4p ⁵5p levels are calculated semiempirically for the RbII-MoVII isoelectronic sequence.     

Radiative constants in the spectra of ions of the erbium isoelectronic sequence

The probabilities of the 4f ¹³6p→4f ¹³5d lectric dipole transitions and the lifetimes of levels of the 4f ¹³6p and 4f ¹³5d configurations are calculated for spectra of ions Yb III, Lu IV, Hf V, and Ta VI of the erbium isoelectronic sequence. The wave functions of the intermediate coupling scheme, necessary for calculating the relative line strengths, are obtained semiempirically from experimentally measured energy intervals between fine-structure levels. To pass to the absolute values, the radial integrals of transitions, evaluated with the Hartree-Fock functions, are used.     

Photoionization of positive ions: Helium to neon isoelectronic sequences

Curves of calculated continuous oscillator strengths for the ground state configurations of positive ion members of two- to ten-electron systems are presented.     

Radial sternheimer shielding-antishielding for He,Ne, and Ar isoelectronic series

Sternheimer quadrupole shielding-antishielding factors γ(r) are reported for the positive ions of B³⁺, Al³⁺, Ca²⁺ and Sc³⁺ for the first time. The trends in γ(r) within the isoelectronic series corresponding to He, Ne and Ar atoms, respectively, are discussed by combining the present results with those reported earlier.     

The backscattering of low energy ions and surface structure

Low energy ion scattering (< 2 keV) in combination with LEED allows surface structure analysis in the case of gases adsorbed on single crystal surfaces. Strong shadowing and anisotropic effects observed are used to estimate the position of the adsorbed species. These techniques may also be extended to study adsorption on polycrystals. For the study of the faces of polar crystals multiple scattering effects in conjunction with shadowing offer a method of surface structure analysis. Surface relaxation effects may possibly be successfully measured by high energy (100 keV – 2 MeV) ion scattering making use of channelling and blocking effects.     

Energy and fine structure of the lithium isoelectronic sequence

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Track structure in dielectric and semiconductor single crystals irradiated by heavy ions with high level of inelastic energy losses

The phenomenological model of the track formation processes during a heavy ion passing through materials is discussed. This model is based on the scanning tunneling and electronic microscopy investigations of diamond single crystals and stainless steel subjected to ⁴⁰Ar, ⁸⁴Kr and ¹²⁹Xe ion irradiation with energies in the MeV region. The energy and temperature criteria when crater formation on the surface during the heavy ion irradiation takes place are introduced.     

Experimental evidence for the influence of the atomic shell structure on the energy loss of high energy heavy ions in matter

Secondary electron yield measurements for ²⁵²Cf fission products in carbon foils reveal significant deviations for the electronic stopping cross section from semiempirical predictions. This effect may correspond to the Z₁ oscillations observed previously at much lower ion velocities.     

Spectroscopic constants of VUV laser transitions in ions of the palladium isoelectronic sequence

Spectroscopic characteristics of ions of the palladium isoelectronic sequence with nuclear charge Z=50–63 are theoretically studied. The Pd-like scheme of x-ray lasers is one of the most efficient schemes. Optical transitions promising for the development of lasers operating in the vacuum ultraviolet region are determined. The wavelengths and probabilities of these radiative transitions are presented, along with their cross sections and the rates of electron-impact excitation of the active levels. The results obtained are compared with experimental data and calculations available in the literature.