Dissociative electron attachment to hydrated single DNA strands.

The present experiments concern electron interactions with a film of short single strands of DNA covered by 3 monolayers of water, which corresponds to 5.25 water molecules per nucleotide. We report on the desorption of H{-}, O{-}, OH{-} from this target induced by 3-20 eV electrons. Below 15 eV, these anions emanate principally from a new type of dissociative core-excited transient anions formed via electron capture by a DNA- H2O complex. A smaller portion of the H{-} desorption signal arises from weakly bonded H2O molecules. The overall anion yield from DNA is increased by a factor of 1.6 owing to the presence of water.