Alignment of Kr +(3d [formula omitted], [formula omitted]) and Xe +(4d [formula omitted], [formula omitted]) after proton impact ionization in the energy range 40–300 keV

Abstract

We have measured the alignment parameter ▪ of Kr +(3d 3 2 , 5 2 ) and Xe +(4d 3 2 , 5 2 ) ions after impact ionization by protons via the non-isotropic emission of Auger electrons. The energy range of protons was ▪ = 40–300 keV which corresponds to the ranges of reduced velocity ▪ = 0.48–1.31 for krypton and ▪ = 0.56–1.54 for xenon. In the case of Kr(3d 3 2 ,3d 5 2 ) ionization the ▪ values showed a resonance-like behaviour with maximum of ▪ = 0.24 at ▪ ≈ 0.8. In the case of Xe(4d 3 2 ,4d 5 2 ) ionization the maximum value of ▪ was smaller and shifted to smaller ▪ as compared with Kr(3d). The comparison with theoretical ▪ values calculated by Berezhko et al. for the direct (Coulomb) ionization indicated that in both cases ionization by electron capture also contributes non-negligibly to the cross section and to the alignment parameter.