The Dissociative Electroionization of Ammonia and Ammonia-d3. I. The NH+ and NH2+ dissociation channels.

The dissociative electroionization of NH3 (ND3) in the NH2+ (ND2+) and NH+(ND+) dissociation channels is investigated in the 15-50 eV electron energy range. The translational energy distributions of ND2+ (NH2+) exhibit several components whereas NH+ only shows a continuous broad distribution. For both ions a kinetic energy-versus-appearance energy diagram is obtained and discussed. The predissociation of the Jahn-Teller split NH3+(A2E) state produces both ions at their lowest threshold. At higher energies dissociative autoionization (in the 22 eV region), dissociative ionization through the NH3+(B2A1) state (in the 24-30 eV region) as well as by Coulomb repulsion of doubly ionized states (in the 35-50 eV region) produce NH2+(ND2+) and NH+ with large amounts of kinetic energy. Some arguments are brought forward to indicate that the former value of the NH2-H dissociation energy is overestimated.