INELASTIC INERT-GAS ION COLLISIONS WITH METAL TARGETS - REARRANGEMENTAND ADSORBATE EFFECTS

Results of recent studies of inert gas ion scattering on metal surface s obtained in this laboratory and elsewhere are briefly reviewed. Thes e have focussed on a study of He, Ne and Ar ion scattering on Na, Mg, Al and Si surfaces for energies in the 500 eV to 15 keV energy range. Measurements of scattered ion and neutral energy and angular distribut ions, charge fraction determinations and electron and photon spectrosc opy results are reported. These demonstrate the role of electronically inelastic ''binary'' small impact partameter collisions with surface atoms. These are responsible for production of singly and doubly excit ed states and ionisation. The results of ion solid collisions are anal ysed and compared to results of gas phase studies of similar collision al systems. Analogies and some major differences are pointed out. The main trends in excitation processes follow the prediction of the molec ular orbital prtomotion model, at least insofar as the prediction of t he type of excited particle produced: projectile or target. This sugge sts that the primary orbital promotion mechanism is the same. Signific ant differences are encountered and have been discussed in terms of el ectron capture and loss processes involving the excited species result ing from the binary collision. The existence of core rearrangement pro cesses have been shown to exist on the example of Ne2+ D-1 to P-3 rear rangement. Models of this core rearrangement process have been propose d. The presence of adsorbates has been shown to modify the outcome of scattering. This is partly due to collisions with both metal target at oms and adsorbate atoms, leading to a modification of the primary exci tation process. Further modifications occur due to a change in the sec ondary electron loss and capture processes leading to a modification o f the final state distributions.