State-selected dissociation of cis-HONO(Ã A″): Effect of intramolecular hydrogen bonding

The influence of intramolecular hydrogen bonding on the photodissociation of cis-HONO is probed via measurements on the OH fragment ejected by specific ---N=0 stretching (ν₂) vibrational levels of the à state. Due to hydrogen bonding between the H atom and the terminal oxygen, the ν₂ motion is coupled to the in-plane HON bend ν₃. Since the latter evolves into fragment rotation, the rotational energy and anisotropy of the OH product increases with the number of ν₂ quanta. By contrast, ν₂ in trans HONO is a relatively isolated ---N=O vibration and thus does not influence the OH photofragment's properties.