Calculated generalized oscillator strengths for monopole, dipole, and quadrupole discrete and continuous spectrum excitations in Ne, Ar, Kr, and Xe are presented. The results cover the broad range of transferred energy $\omega ,\hspace{0.5em}0<~\omega <120\mathrm{}\hspace{0.5em}\mathrm{Ry}$ and momentum $q,\hspace{0.5em}0<~q<\mathrm{}2\mathrm{}\hspace{0.5em}\mathrm{a}.\mathrm{u}.$ The calculations were performed in the one-particle Hartree-Fock approximation and with account of many-electron correlations. The latter effects are included via the random phase approximation with exchange, proving to be important in all dipole, monopole, and quadrupole channels as well as in all the domains of the transferred energies and momenta considered. Particularly important are the many-electron correlations at high q values, where new additional purely correlational maxima and minima appear. These results, particularly the maxima and minima are expected to stimulate experimental activity in this domain of atomic physics.

Using high-dispersion spectral observations of HD 101065 (Przybylski's star) we have identified the lines of heavy radioactive elements with atomic numbers from 84 to 99 in the spectrum of the star. We found the lines of all these elements except At (Z=85) and Fr (Z=87). We try to explain a presence of such heavy species in the atmosphere of this star as a result of radioactive decay of Th and U nuclei and neutron capture process producing some transuranium isotopes. The necessary conditions for these processes to work may appear due to atomic diffusion and favorable accumulation of the thorium and uranium nuclei in the upper of the PS atmosphere.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The article is devoted to a brief description of the ATOM computer program system, designed to study the structure, transition probabilities and cross sections of various processes in multielectron atoms. The theoretical study was based on the concept of a computational experiment, the main provisions of which are discussed in the article. The main approximate methods used in the system of programs for taking many-electron correlations into account and determining their role in photoionization processes, elastic and inelastic electron scattering, the decay of vacancies, and many others are presented. The most significant results obtained with this software are listed.

We theoretically study the positron elastic scattering by an atom with a multielectron semifilled subshell in its structure. We focus on gaining the initial insight into the specifics of such a process. The positron scattering by the Mn(…3d ⁵ 4s ² , ⁶ S) atom with a 3d ⁵ semifilled subshell (e ⁺ + Mn scattering) is chosen as a case study. We account for both the electron correlation and the formation of a e ⁺ + e ⁻ virtual positronium (Ps) in the intermediate states of the e ⁺ + Mn system. Electron correlation is taken into account in the framework of the self-energy part of the scattering positron Green function generalized for the application to semifilled-shell atoms. The influence of the virtual Ps formation on the positron scattering is taken into account by the reduction of the energy of the virtual positron plus atomic-excited-configuration states by the Ps-binding energy, to a reasonable approximation. We unravel the importance and specificity of the influence of both the virtual Ps and electron correlation on e ⁺ + Mn elastic scattering. We demonstrate spectacular differences between the electron and positron scattering processes.