Decay dynamics of the predissociating high Rydberg states of NO

The dynamics of predissociating high molecular Rydberg states of NO below t he lowest ionization threshold is computed in the presence of a weak extern al dc field using a quantum theory based on an effective Hamiltonian formal ism. The core-electron interaction affecting the low l states (l less than or equal to 2) is taken into account by molecular quantum defect theory, wh ile for the high l states (l greater than or equal to 2), a long range mult ipolar expansion is used to describe the effect of the anisotropy of the mo lecular core. Time- and frequency-resolved ZEKE spectra are computed. In th e energy range investigated, the decay kinetics of the ZEKE intensity is fo und to exhibit two time scales, which differ by more than an order of magni tude. The short decay constant typically falls in the submicrosecond range and is in agreement with previous experimental results and computations. In addition, our computations predict a long-time component, which decays in the tens of microseconds range. The two decay times are discussed in terms of the short and long range interseries dynamics, in terms of the strength of the external dc field, and in terms of the nature of the bottlenecks in phase space for a predissociating molecular core with a rather large rotati onal constant (BNO+ = 1.9842 cm(-1)). It is found that for this particular case where all series are coupled to the fragmentation channels through a l ow l bottleneck, the predissociation process does not quench the long time component in the decay kinetics. The reason is that the interplay between t he interseries coupling and the external dc field leads to a shift of the d ecay constants to larger values together with an enhancement of the weight of the long time component in the decay kinetics. Special attention is devo ted to the role of the dipolar interaction and its synergy with the externa l dc field.