Ionisationsquerschnitt von OV gegenüber Elektronenstoß unter teilweiser Berücksichtigung des Austauschs

Abstract

The ionization cross-section of highly ionized oxygen, O⁴⁺, is calculated according to the “distorted-wave” method. Exchange between the scattered and the ejected electron is taken into account as far as it is of long range nature. It is shown that contributions of high total angular momentum L are essential, L=0 giving only 3% of the total cross-section. This result should qualitatively be the same for all highly ionized atoms, whereas the following seems to be a special feature of O V ionization: for energies around twice the ionization energy the contributions of the optically allowed transitions of the ejected electron (angular momentum l_ej=1) are relatively small. The contributions of l_ej =0, 1, 2 and 3 are about 16%, 18%, 24% and 19% respectively for E=20.13.6 eV=2.39 × Ionization energy. The maximum cross section is 0.112 at. u. = 0.31 ·10^-18 cm² for electrons of 310 eV kinetic energy (2.8 × ionization energy). It is about twice as large as given by the ELWERT formula.