Laser photofragment spectroscopy of NO+. I. Predissociation of the 2 3Π state

NO+ ions, produced by electron impact on NO, are observed to predissociate into O+(4S0)+N(4S0) when irradiated by a dye laser at wavelengths between 6600–5650 Å. The highly structured wavelength dependence of the photofragments reflects absorptions from three vibrational levels in a long-lived NO+ electronic state to 20 vibrational levels of a predissociated electronic state. The transitions are tentatively identified as 2 3Π(v′ = 0–19)←b′ 3Σ−(v″ = 8–10). The weakly bound 2 3Π state is found to lie 0.698–0.925 eV above the lowest separated atom limit of NO+ and to adiabatically correlate to the N+(3P)+O(3P) limit. This state is also found to be homogeneously perturbed, most likely by the 3Π state arising from the O+(4S0)+N(2D0) limit, and to be predissociated by the α 5Σ+ state. The predissociation lifetimes for all rotational levels in v′ = 0–8 are ≥1.6 ns. Perturbations in b′ 3Σ−(v = 9) are discussed.