Formyl radical (HCO) is an important intermediate in combustion, atmospheric, and interstellar chemistry. Its ground state X2A' is bent and the first excited state A2A" is linear, and they are a Renner-Teller (RT) pair that are a degenerate 2Π state at linear configuration. The A2A"-X2A' predissociation dynamics of the HCO radical is examined at a state-to-state level in a combined experimental and theoretical study. The complete CO (v, J) product state distributions from various vibrational levels of the A2A" state are obtained from the H-atom product translational energy distributions. The CO product rotational distributions are highly inverted, and furthermore, intensity oscillations at high J states are observed. The quantum reaction dynamics show that the oscillations in the CO product-state distributions are attributed to an interference effect stemming from unique features on the ground-state potential energy surface (PES) of HCO, following the decay of the excited A2A" state to the ground X2A' state at linearity (via the RT coupling). This interference effect is exquisitely sensitive to the PES and thus can be used to probe dynamically important regions of the reactive PES. Detailed predissociation dynamics will be discussed.

Dynamical interference in the vibronic bond breaking reaction of the formyl (HCO) radical

ACS Spring 2022

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