Interactions of neutral and singly charged keV atomic particles with gas-phase adenine molecules

KeV atomic particles traversing biological matter are subject to charge exchange and screening effects which dynamically change this particle's effective charge. The understanding of the collision cascade along the track thus requires a detailed knowledge of the interaction dynamics of radiobiologically relevant molecules, such as DNA building blocks or water, not only with ionic but also with neutral species. We have studied collisions of keV H+, He+, and C+ ions and H-0, He-0, and C-0 atoms with the DNA base adenine by means of high resolution time-of-flight spectrometry. For H-0 and H+ we find qualitatively very similar fragmentation patterns, while for carbon, strong differences are observed when comparing C-0 and C+ impact. For collisions with He-0 and He+ projectiles, a pronounced delayed fragmentation channel is observed, which has not been reported before. (C) 2007 American Institute of Physics.