Focused ion beams
are becoming important tools in nanofabrication.
The underlying physical processes in the substrate were already explored
for several projectile ions. However, studies of ion interaction with
precursor molecules for beam-assisted deposition are almost nonexistent.
Here, we explore the interaction of various projectile ions with iron
pentacarbonyl. We report fragmentation patterns of isolated gas-phase
iron pentacarbonyl after interaction with 4He+ at a collision energy of 16 keV, 4He2+ at
16 keV, 20Ne+ at 6 keV, 20Ne4+ at 40 keV, 40Ar+ at 3 keV, 40Ar3+ at 21 keV, 84Kr3+ at 12 keV,
and 84Kr17+ at 255 keV. These projectiles cover
interaction regimes ranging from collisions dominated by nuclear stopping
through collisions dominated by electronic stopping to soft resonant
electron-capture interactions. We report a surprising efficiency of
Ne+ in the Fe(CO)5 decomposition. The interaction
with multiply charged ions results in a higher content of parent ions
and slow metastable fragmentation due to the electron-capture process.
The release of CO groups during the decomposition process seems to
take off a significant amount of energy. The fragmentation mechanism
may be described as Fe being trapped within a CO cluster.
DNA constituents are effectively decomposed via dissociative electron attachment (DEA). However, the DEA contribution to radiation damage in living tissues is a subject of ongoing discussion. We address an essential question, how aqueous environment influences the DEA to DNA. In particular, we report experimental fragmentation patterns for DEA to microhydrated 2-deoxycytidine 5-monophosphate (dCMP). Isolated dCMP was previously set as a model to describe mechanisms of DNA-strand breaks induced by secondary electrons and decomposes primarily by dissociation of the C-O phosphoester bond. We show that hydrated molecules decompose via dissociation of the C-N glycosidic bond followed by dissociation of the P-O bond. This significant change of the proposed mechanism can be interpreted by a reactive role of water in the postattachment dynamics. Comparison of the fragmentation with previous macroscopic irradiation studies suggests that the actual contribution of DEA to DNA radiation damage in living tissue is rather small.
We investigate the effect of microhydration on electron attachment to thiophenols with halogen (Br) and nitro (NO2) functional groups in the para position. We focus on the formation of anions...
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