Photoabsorption in the statistical model of an atom: Noninteracting electron model and effect of polarization

Abstract

Two approaches to the description of photoabsorption of a multielectron atom are considered, viz., the semiclassical method for solving the kinetic equation by determining the Fourier components of the dipole moment for electrons disregarding polarization of the atom (the noninteracting electron model, NEM) and the method for calculating the cross section of photoabsorption at complex atoms, which is based on solving the kinetic equation using the method of particles taking into account polarization (direct particle method, DPM). During the development of the NEM, the problem of classical emission of radiation by a charged particle moving in an arbitrary centrosymmetric potential was solved. The NEM and DPM were used for calculating the distribution of oscillator strengths df/dω of a neutral Thomas-Fermi atom for the entire Thomas-Fermi frequency range 27 eV ≪ ħω ≪ 27Z2 eV. Comparison of the results obtained using these two approaches has made it possible to estimate the magnitude of polarization effects. The effect of polarization is pronounced only at low frequencies, while the mean characteristics (including the logarithmic mean excitation energy I) are not strongly affected by polarization. When polarization is taken into account, the value of this quantity is I = 7.95Z eV and is close to the experimentally determined range. The results of calculation of df/dω are compared with experimental data.