Rotational Modulation of Ã2A″-State Photodissociation of HCO via Renner-Teller Nonadiabatic Transitions.

By examining the product-state distribution of a prototypical nonadiabatic predissociation system, HCO(Ã2A″-X̃2A'), we demonstrate that the dissociation dynamics is strongly modulated by parent rotational quantum numbers. The predissociation of the nominal (νC-H = 0, νbend, νC-O = 1) vibronic levels of the Ã2A″ state surprisingly gives rise to both vibrational ground and excited states of the CO product, despite the assumed spectator nature of the CO moiety. This anomaly is attributed to the dependence of the lifetime of the vibronic resonance facilitated by the Renner-Teller interaction on the parent rotational angular momentum quantum numbers coupled with transient intensity borrowing from nearby vibronic resonances with νC-O = 0. This unique phenomenon is a purely quantum mechanical behavior that has no classical analogue.