The effect of direct excitation on K-shell vacancy production in Cu-Fe collisions

Recently, Stahler and Presser (1981) published target thickness dependent inner-shell vacancy production probability measurements on Cu-Fe collisions. They concluded that direct excitation cannot contribute appreciably to this probability. In the present letter their data are reanalysed assuming direct excitation to be the only relevant vacancy production mechanism besides rotational coupling. It is found that this analysis yields perhaps better agreement with the data than the conclusion of the original paper.