Orbiting resonances in formaldehyde reveal coupling of roaming, radical, and molecular channels

Quantum nature of roaming dynamics Despite intense study, roaming systems have been generally treated classically and their dynamics have been assumed to be ergodic. Foley et al . provide a combined experimental and theoretical study of the photodissociation of formaldehyde near the threshold for radical production. Their observations revealed a strong dependence of the degree of roaming on the rotational state of the molecule that is excited, which is indicative of an important role for quantum orbiting resonances. This study demonstrates unexpected, non-ergodic roaming dynamics in the prototypical roaming system that does not fit into the conventional classical picture, subject to further studies in other systems. —YS