Classical resonance absorption in atoms and the theory of optical constants in XUV range

Abstract

The theory of linear response of the Thomas-Fermi atom to an external monochromatic field is developed in some approximation. This approximation corresponds to the high frequency limit of the exact theory and can be formulated in terms of the classical problem of polarizability of inhomogeneous particles. The main specific features of this problem as applied to atomic polarizability in the XUV are: (1) the wavelength is much larger than the particle's size; (2) there is a point inside the particle where the dielectric constant is zero. The resulting equations have been solved for various atomic electron density distributions. The photoabsorption cross section and the real part of atomic polarizibility are obtained. It can be shown that calculated in such a way they automatically satisfy the Kramers-Kronig equations. This theory can be considered as a natural generalization of S. Lundqvist's approach.