Dissociative attachment from vibrationally and rotationally excited HCl and HF

An electron impact mass spectrometer is used to study dissociative attachment in HCl, DCl, and HF at incident energies 0–4 eV. Target molecules in different excited nuclear states are prepared with an iridium oven source. The cross sections for Cl−/HCl, Cl−/DCl, and F−/HF all show an order of magnitude increase with each increase of vibrational quantum (v=0, 1, and 2). In Cl−/HCl the threshold cross section for the v=2 level at 0.1 eV reaches (7.8±4.7)×10−15 cm2. Together, this large cross section and the recent potential-energy-curve calculations of HCl and HCl− show that the conventional theory of dissociative attachment may not be applicable here. A new mechanism for dissociative attachment is suggested.