Differential cross section for dissociative attachment in HCl: Cl⁻and H⁻formation

A modified electron impact spectrometer is used to study Cl - and H - formation in HCl by dissociative attachment. It is shown that the Cl - ion yield exhibits a small, new structure located at the maximum of the main peak in addition to the well known structure on the high-energy tail at the vibrational levels of HCl. The H - ion yield exhibits two peaks at 7.1 and 9.3 eV. The first one is structureless with a non-vertical onset and the angular distribution of the H - is characteristic of a d sigma wave. These results indicate that H - formation in the energy range of this peak proceeds via a repulsive 2 Sigma + HCl - state. The second peak, which proceeds via a 2 Pi HCl - state, exhibits a structure on the high-energy tail and the angular distribution of the H - ions is characteristic of a d pi wave. The structures in this peak are attributed to the interaction of the 2 Pi state of HCl - with the series of Feshbach resonances associated with Rydberg states of HCl.