Electron Impact Excitation of the c 3Πu States of H2 and D2 by a Trapped-Electron Method

Electron impact excitation of H2 and D2 within 0.05 eV of threshold is studied with a trapped-electron method. An ac RPD technique is used to achieve energy resolution better than 0.1 eV. A series of trapped-electron peaks is resolved in the 11.7- to 13.5-eV range. These are identified as vibrational levels of the c 3Πu state. In this energy range, excitation of other states (both singlet and triplet) near threshold is found to be weak by comparison. Several peaks observed in the 13.8- to 15.4-eV range could not be assigned to excitation of vibrational levels of a single electronic state.