L. V. Chernysheva

Interference effects in photoionization of noble gas atoms outer s-subshells

A strong influence of ns2np6 → ns2np5 ϵd transition on the outer ns subshell photoionization cross section of noble gas atomsis demonstrated.

Angular distribution of photoelectrons with many-electron correlations

Abstract The angular distribution of electrons in the noble gas photoionization is calculated with many-electron correlations taken into account in the random phase approximation with exchange.

Computation of atomic processes : a handbook for the ATOM programs

Overview essential physics of the ATOM system mathematical description of atomic properties radial self-consistent Hartree-Fock equations radial self-consistent hartree-fock-dirac equations radial Hartree-Fock equation for the frozen core the choice of wavefunctions the coefficients in the Hartree-Fock equation photoionization, oscillator strengths and polarizability generalized oscillator strengths electron-impact ionization generalized oscillator strengths with PCI inner-shell photoionization with PCI near-threshold ionization self-energy part of the one-particle green function scattering phases and electron wavefunctions taking account of the self-energy part the Auger decay widths of atomic levels probability of the doubled Auger decay one-photon decay of two-hole states electron-induced triplet level excitation high-energy projectile Bremsstrahlung the photoabsorption cross-section the features of Muon capture the structure of the ATOM system results of calculations.

Relative intensities in x-ray photoelectron spectra. Part VI. The spectra of He(I), He(II), Y Mζ and Zr Mζ☆

The 2s- and 2p-electron photoionization cross-sections at photon energies up to 190 eV have been calculated, using the RPAE method for averaged configurations of the C, N, O and Ne atoms. The RPAE method ensures a more accurate relation between the cross-sections, 2s/2p, than that obtained using the Hartree—Fock method. Within the framework of the Gelius—Siegbahn model, but with the use of theoretical atomic cross-sections, we have calculated the photoionization cross-sections for He(I), He(II), Y Mζ, Zr Mζ for CH4, C2H6, C3H8, C2H4, C2H2, NH3, H2O, CN−, N2, CO, CO2, N2O and NO2− molecules. For CO, N2, CO2, N2O and H2O molecules, a comparison is made between the theoretical and experimental cross-sections for hν < 60 eV. The calculated absolute and relative values of the molecular-orbital cross-sections are in reasonable agreement with experiment, especially at hν ⩾ 40 eV. The calculations correctly reproduce the change in intensities under the transition He(I) → He(II). We have shown that our calculations have a significant advantage over those performed using the PW and OPW approximations. It is shown for NO, N2, CO, H2O, CH4, NH3 and N2O molecules that the total photoionization cross-section calculated taking into account the real structure of the molecular orbitals is in better agreement with the experimental photoabsorption cross-section than is the sum of the cross-sections for the atoms in a molecule.

Dramatic distortion of the 4d giant resonance by the C60 fullerene shell

The photoionization cross section for the endohedral Xe@C60 atom is investigated within the framework of representing the C60 by a delta-type potential. Results demonstrate that in Xe@C60, the 4d giant resonance is distorted significantly when compared with that of the isolated Xe atom. The reflection of the photoelectron waves by the C60 causes strong oscillations in the photoionization cross section resulting in the replacement of the Xe 4d giant resonance by four prominent peaks. The approximation of C60 by an infinitely thin real potential preserves reasonably well the sum rule for the 4d electrons but modifies the dipole polarizability of the 4d shell.

Single and double photoionisation in Xe and Ba above the 4d threshold

The authors advance and examine a new mechanism which strongly influences the photoionisation processes above the 4d threshold in Xe and Ba. It is shown that the elastic and inelastic scattering of the inner-shell photoelectron by the outer-shell electrons determines the rate of single and double ionisation, decomposing the cross section of the inner-shell photoabsorption into these two channels. The results of these calculations are in good agreement with experimental data.

Giant resonances of endohedral atoms

It is demonstrated for the first time that the effect of a fullerene shell on the photoionization of a “caged” atom in an endohedral can result in the formation of giant endohedral resonances or GER. This is illustrated by the concrete case of the Xe@C60 photoionization cross section that, at 17 eV, exhibits a powerful resonance with total oscillator strengths of about 25. The prominent modification of the 5p6 electron photoionization cross section of Xe@C60 takes place due to the strong fullerene shell polarization under the action of the incoming electromagnetic wave and the oscillation of this cross section due to the reflection of the photoelectron from Xe by the C60. These two factors transform the smoothly decreasing 5p6 cross section of Xe into a rather complex curve with a powerful maximum for Xe@C60, with the oscillator strength of it being equal to 25. We also present the results for the dipole angular anisotropy parameter that is strongly affected by the reflection of the photoelectron waves, but not modified by C60 polarization.

Many-electron correlations in negative-ion photodetachment

Photodetachment cross sections for Na-, Ag-, I- and Si- negative ions, calculated using the random phase approximation with exchange are presented. The cross sections for outer and nearby inner subshells are strongly influenced by intrashell and intershell electron correlations. It is found that in some particular cases correlations radically change the photodetachment cross sections.

Photoionization cross section of 4d10 Xe, Cs and Ba subshells with account of electron shell rearrangement

Abstract It is demonstrated that the account, along with many-electron correlations in RPAE method, of the electron shell rearrangement in the process of photoionization, permits to achieve a reasonable agreement between theory and experiment for the 4d10 subshell cross sections of Xe, Cs and Ba atoms.

Elastic scattering of slow positrons by helium

The s-, p-, d- and f-wave phase shifts for elastic scattering of slow positrons by He are calculated using a simplified version of the random phase approximation with exchange, with the virtual positronium formation effect taken into account.