Ionization Cross Sections of the Elements Calculated from Mean-Square Radii of Atomic Orbitals

Abstract

Relative ionization cross sections for single ionization by electron impact on free gaseous atoms have been calculated by utilizing a summation of the mean-square orbital radii of outer electrons. A previous calculation of the cross sections by Otvos and Stevenson was in only fair agreement with experimental data due to the use of incorrect mean-square radii, and to the method of summation of electron-shell contributions to the total cross sections. Hartree—Fock calculations of orbital wavefunctions have been carried out for all of the elements. Mean-square radii of atomic orbitals from the Hartree—Fock calculations were corrected approximately for relativistic effects. The ionization cross sections obtained from the summations were normalized at argon and compared with experimental values. The computed maximum cross sections are a considerable improvement over past theoretical values.