Ion pair dissociation from N2O followed by autodetachment of N−(1Dg) Original Research Article

A novel kind of ion pair dissociation, where autodetachment from the negative ion follows charge separation, has been observed in N2O by velocity imaging photoionization coincidence spectroscopy. At a photon energy of 16.85 eV, electrons with a kinetic energy of ∼1.5 eV are found in coincidence with vibrationally excited NO+(X 1Σ+). The formation mechanism is assigned as N2O(X 1Σ+)+hν→NO+(X 1Σ+)+N−(1Dg)→NO+(X 1Σ+)+N(4Su)+e−, on the basis of the energetics of the system and the kinetic energy distribution of the NO+(X 1Σ+). Asymmetry parameters β for the electrons and NO+ ions are −0.12±0.02 and −0.03±0.01 respectively. Lack of angular correlation between the electron and NO+ directions is interpreted as showing autodetachment at very long range, consistent with the very long calculated lifetime of the excited N− ion.