The energy dissipation and femtosecond dynamics due to fast heavy ions in matter is critically reviewed with emphasis on possible mechanisms that lead to materials modi cations. Starting from a discussion of the initial electronic energy deposition processes, three basic mechanisms for the conversion of electronic into atomic energy are investigated by means of Auger electron spectroscopy. Results for amorphous Si, amorphous C and polypropylene are presented and discussed. Experimental evidence for a highly charged track region as well as for hot electrons inside tracks is shown. As follows mainly from Auger electron spectroscopy, there are strong indications for di erent track production mechanisms in di erent material
