Photodissociation spectroscopy via a rovibrational resonance in intense UV pulses

Abstract

Photodissociation dynamics via a rovibrational resonance in intense UV pulses is investigated theoretically, using a showcase ${\text{CH}}^{+}$ molecule promoted to the $\text{C}\phantom{\rule{0.16em}{0ex}}^{1}\mathrm{\ensuremath{\Sigma}}^{+}$ valence excited electronic state with a potential barrier, thus giving access to study shape resonance controlled by the pulse frequency. Simulations of the kinetic energy release (KER) and angular distribution of the photofragments (ADP) spectra show dramatic differences for the cases when the pulse is tuned on and off the rovibrational resonance. It shows that as the increasing pulse intensity for the transitions to shape resonance, the KER spectra develop into new and higher energy peaks overlying on the broadened background, which is explained by the involvement of other resonances with higher partial waves through electronic Rabi flopping between the ground and excited electronic states. Those nonlinear contribution increases drastically the probability of photofragmentation along the laser polarization in the ADP spectra. The coincident KER-ADP spectra reveal clearly the correlated dynamics in the vicinity of the dissociation barrier. The present work opens possibilities for the manipulation of ultrafast photodissociation dynamics with the help of resonance states in the continuum.