Resonant neutral-particle emission in collisions of electrons with protonated and sodiated nucleotide monocations in a storage ring

Electron-ion collisions have been studied for protonated and sodiated single-strand dinucleotide monocations with various base compositions and sequences by using an electrostatic storage ring equipped with a merged-electron-beam device. Plots of neutral-particle production rates against collision energy show typical electron-capture-dissociation profiles, which increase for energies close to zero and contain a bump at high energies. The height of the resonant bumps varies with the number of Na+ ions as well as the base composition and sequence; in most cases, the height increases with an increase in the number of Na+ ions. Molecular mechanics and semiempirical quantum-chemical calculations suggest that the rate is correlated with various base-base interactions.