Evidence for predissociation of N2 a 1Πg(v≥7) by direct coupling to the A′ 5Σ+g state

Predissociation of the (v=7–10) levels of the a 1Πg state in N2 is studied with translational spectroscopy. These levels are produced by the charge-transfer neutralization of a 4 keV energy N+2 beam in sodium vapor and the dissociation fragments are monitored by a time- and position-sensitive detector. Lifetimes of 300, 300, 100, and 230 (±20) ns are measured for a 1Πg(v=7, 8, 9, and 10), respectively. Quantum mechanical calculations based on Fermi’s golden rule give evidence that the predissociation is caused by direct coupling to the continuum of the A′ 5Σ+g state rather than by an indirect mechanism. The a 1Πg–A′ 5Σ+g electronic coupling matrix element is estimated to be 0.44 (±0.03) cm−1. The required change in spin multiplicity suggests that this coupling arises from a spin–spin interaction.