Results of an angle resolved electron spectroscopy study of low keV in
ert gas ion collisions with a Mg surface are presented. Production of
projectile autoionising states is demonstrated to exist not only for t
he previously known Ne case but also for He. The role of these states
in ion production is commented. The characteristics of autoionising pe
ak lineshapes are analysed and suggest a method of obtaining angular d
istributions of inelastically scattered ions.