Rotational state dependence of decay dynamics in the superexcited 7f Rydberg state (υ=1) of NO

The decay dynamics of the 7f Rydberg state (υ=1) of NO has been investigated with laser multiphoton excitation methods; not only NO⁺ ions generated by autoionization, but also fragment nitrogen atoms produced by predissociation have been directly probed. The fragment atoms have been found to populate both the 2_p^{3 2}D_J and 2 _p^{3 4}S_3/2 states. Population yield in the ⁴S state shows strong dependence on each 7f rotational level of NO, and this dependence is remarkably correlated with autoionization yield, while no such significant dependence exists for the ²D state. From the fact that only odd ℒ levels generate the ⁴S state, dissociative states causing this predissociation process have been identified as Σ⁺ states. Through detailed analysis, it has been shown that the predissociation rate of this channel is much larger than the autoionization rate, and that the N (²D) -generating predissociation is also mainly caused by dissociative Σ⁺ states. Moreover, it has been found that a major part of the total decay rate of each rotational level is strongly correlated with magnitude of its fσ character. From these facts, it has been concluded that the decay process in the 7f state is mainly governed by predissociation due to direct coupling with dissociative Σ⁺ valence states, which have been identified as A′ ^{1 2}Σ⁺ and I₂Σ⁺ for the N(⁴S)- and N(²D)-generating predissociation channels, respectively.