High resolution multiple electron impact ionisation of He, Ne, Ar, Kr and Xe atoms close to threshold: Appearance energies and Wannier exponents

Abstract We have determined appearance energies AE(X n + /X) for the formation of multiply charged He, Ne, Ar, Kr and Xe ions up to charge state n =2 (He), n =4 (Ne), n =6 (Ar), n =6 (Kr) and n =8 (Xe) using a recently commissioned high-resolution electron impact ionization mass spectrometer. The data analysis is based on the Marquart–Levenberg algorithm, involving an iterative, non-linear least-squares fitting of the threshold data assuming a 2-function or a 3-function fit based on a Wannier-type power law. This allows us to extract the relevant AEs and corresponding Wannier exponents.