N(4S), N(2D), and N(2P) yields in predissociation of excited singlet states of N2

Abstract

Predissociation in several singlet valence and Rydberg states of molecular nitrogen has been investigated using photofragment spectroscopy. We report here measurements of the yields of the atomic fragment products N(4S0), N(2D0), and N(2P0) from predissociation of specific rotational levels in the b′ 1Σu+ (v=9–13), c′ 1Σu+ (v=3,4), c 1Πu (v=3,4), and o 1Πu (v=3) states of N2. These states are prepared by laser excitation from the metastable a″ 1Σg+ (v=0) level in a fast (3 keV) molecular beam. Correlated atomic fragments from single molecular dissociation events are monitored using a position- and time-sensitive detector to obtain a complete and sensitive scheme for all possible N2 dissociation products. Dissociation of the N2 states is found to occur to N(2D0)+N(4S0), and N(2P0)+N(4S0) products; production of N(4S0)+N(4S0) is found not to occur from any of the states investigated here. Branching of the dissociation products between the two active limits is found to be strongly correlated with the energy of the predissociating level: levels lying <112 200 cm−1 above N2 X 1Σg+ (v=0) predissociate primarily to the N(2D0)+N(4S0) limit, while states above this energy primarily predissociate to N(2P0)+N(4S0). This behavior is discussed in terms of the potential energy structure of the triplet states of nitrogen that lead to predissociation.