Multiple Ionization of Ar and Mg by Electron Impact

Abstract

Ionization efficiency curves (IE curves) of Ar and Mg are measured up to 1000 eV by crossed beam method. A mass spectrometer is used for separation of multiply charged ions. Abundance ratios of multiply charged ions to singly charged ion at 500 eV are obtained up to five fold and three fold charge for Ar and Mg respectively. The summations of the IE curves of multiply charged ions agree well with the absolute total ionization curves obtained by other workers. The IE curve of Ar⁺ has two maxima at 45 eV and 90 eV. Remarkable structures are found at 255 eV for Ar³⁺ and Ar⁴⁺ and they are attributed to an Auger process or an electron shake-off caused by the ionization of inner shell electrons. A break at 55 eV for Mg²⁺ is probably attributed to autoionization arising from the excitation of inner shell electron which occurs below 55 eV. The curves for Ar²⁺, Mg⁺ and Mg³⁺ seem to have no structures.