Isotope effects in dissociative electron attachment to the DNA base thymine

Dissociative electron attachment to thymine and two partially deuterated derivatives are studied with high electron energy resolution. For all fragment anions involving hydrogen loss, a dramatically reduced anion yield is measured for loss of D compared to loss of H. For the low-energy vibrational Feshbach resonances this isotope effect reaches a value of 40. Narrow features in the anion yields that previously were assigned to H loss from the N1 site of thymine and concomitant excitation of specific stretching modes are shifted to lower electron energies when deuterium is involved.