Target nuclear charge dependence of 1s²to 1s2p and 1s²to 1s3p excitation cross sections of Fe²⁴⁺projectiles in the intermediate velocity range

Abstract

Excitation cross sections into the 1s2p and 1s3p states of 400 MeVFe24+ projectiles colliding with He, N2, Ar and Kr targets have been extracted from the intensities of helium-like 2P to 1S and 3P to 1S transitions de-exciting the ion after one-electron 1s to 2p and 1s to 3p excitation. The exciting partner being neutral, the capture channel is closed, and these experiments thus give an opportunity to study the pure distortion effect even in the case of quasisymmetric systems at intermediate velocity (Vp/Ve approximately 0.6). A striking feature of the results is the experimental evidence of saturation in the excitation cross section as the nuclear charge of the exciting partner increases. This trend is supported by theoretical predictions of a new method based on the Schwinger variational principle that was developed for that purpose.