Ionisation cross sections of rare-gas atoms by electron impact

Abstract

Normalised values of partial ionisation cross sections for the rare gases (He⁺, Ne⁺-Ne³⁺, Ar⁺-Ar³⁺, Kr⁺-Kr⁴⁺ and Xe⁺-Xe⁵⁺) have been measured from threshold to 1000 eV using a pulsed electron beam and ion extraction technique. The cross sections have been obtained for the singly ionised species by normalising the relative data with the results of Rapp and Englander-Golden (1965) below the onset of production of the doubly ionised species. These cross sections for the singly ionised species have then been used to calibrate the mass transmission efficiency of the ion extraction+analyser+detection system by the relative flow technique. The mass transmission curve thus obtained has been employed to determine the absolute cross sections of the multiply ionised species. Summation of the individual partial cross sections with proper weighting for charge is employed to obtain the total ion cross sections. The measured partial cross sections are fitted to an empirical formula for the ease of future use.