Dissociative electron attachment in uracil: Total anion yield

The total relative yield of anions produced by electron impact on uracil has been measured at energies below ionization. Peaks associated with vibrational Feshbach, shape and core-excited resonances are observed, although the relative sizes differ from those measured using mass analysis. Observation of positive ionization in uracil permits normalization to the ionization cross section. Feil et al. [J. Phys. B: At. Mol. Opt. Phys. 37 (2004) 3013] have used the semi-classical Deutsch–Märk ionization cross section for this purpose. Using the D–M cross section for normalization, we find that the cross section for production of (U–H)− is substantially smaller than their mass selected result.