Calculation of Photoabsorption Cross Section of an Extended Thomas-Fermi Atom

Abstract

Bloch’s hydrodynamic approximation for treating the charge oscillation of an atom is applied to the Thomas-Fermi atom extended by introducing a modified Weizsäcker correction. Normal mode solutions of the oscillation are obtained and the atomic photoabsorption cross section and the logarithmic mean excitation energy are calculated. The differences of the results from those of the simple Thomas-Fermi atom are as follows: (1) The eigenfrequencies of the normal modes consist of one discrete value ω_D (<ω_C) and continuous values between ω_C and ∞, where ω_C is a definite frequency characteristic for an individual atom. (2) The photoabsorption cross section has also a discrete value corresponding to the frequency ω_D and continuous values for frequencies larger than ω_C. (3) The logarithmic mean excitation energy becomes larger.