Dissociative and non-dissociative electron attachment processes are investigated via electron transfer in collisions between velocity selected Rydberg atoms and molecules. Low-energy dissociative electron attachment to BrCN and CBrCl 3, over the temperature range 300 to 450K, is examined, by measuring the velocity and angular distributions of negative ions produced. Measurements for BrCN indicate that electron capture leads to the formation of transient BrCN-* ions that dissociate with a mean lifetime tau ∼20 ps to form CN- product ions. No significant Br - production was observed over the present temperature range. Electron transfer to CBrCl3 leads to the formation of both Cl - and Br- ions. The branching ratio of the reaction pathways dramatically changes with temperature. Investigation of non-dissociative electron attachment to C6H6 indicates that benzene anions are formed with lifetimes of ∼3 ps. Influence of a strong applied electric field on background processes like blackbody photoionization and collisional photo ionization, which complicate studies of Rydberg atom collision processes, is analyzed and the results presented.