Internal excitation mechanisms of neutral atoms and molecules emitted from ion bombarded organic thin films

Resonance enhanced laser photoionization schemes are employed to ionize C₆H₆ molecules and Ag atoms desorbed from Ag{111} by 8 keV Ar⁺ ion bombardment. These schemes allow for probing ground state and internally excited species. Time-of-flight mass spectrometry is utilized to detect the postionized atoms and molecules desorbed in a neutral charge state and for determining their kinetic energy distributions from time-of-flight measurements. We find that internally excited species must originate from near the surface/vacuum interface. The species detected in the ground state may originate from deeper in the sample matrix, as well as from the surface.