Desorption induced by electronic transitions (DIET) of neutral fragments from chemisorbed biological molecular systems

Low-energy electron stimulated desorption of neutral fragments from oligomers chemisorbed onto a gold surface is investigated within the 1–30 eV range. The oligonucleotides are anchored to the surface via a sulfur-bound technique similar to the procedure used in molecular self-assemblies. We show that under electron impact the dissociation of DNA bases occurs, leading to the production of CN, OCN and/or H2NCN neutral species, which are the most intense observable yields. The incident electron energy dependence of these desorbed neutral species exhibits typical signatures of dissociative electron attachment initiated by the formation of shape and core-excited resonances below 20 eV, whereas usually non-resonant processes (i.e. dipolar dissociation or dissociative ionization) become predominant above 20 eV.