Abstract
Alignment of the L3 shell in argon has been measured for electron and proton impact in the region of electron threshold and compared with previous experimental data and theoretical calculations. The measured alignment at electron threshold is negative in the proton impact case. For electron impact, an increasingly positive alignment is found as the velocity is decreased. However, for electron impact velocities less than 20% above threshold, no alignment analysis was possible because of observed Auger line broadenings. By studying the broadening as a function of velocity above threshold and comparing electron- and proton-induced spectra for equal velocities, the authors have described the broadening as arising from a post-collision interaction between the ionised 2p and emitted Auger electrons.