Roaming in Restricted Acetaldehyde: a Phase Space Perspective

Recent experimental and theoretical results show many molecules dissociate in a slow and complicated manner called roaming, that is due to a mechanism independent of the mechanisms for molecular and radical dissociation. While in most molecules the conventional molecular mechanism dominates roaming, acetaldehyde stands out by predominantly dissociating to products characteristic for roaming. This work contributes to the discussion of the prominence of roaming in (restricted) acetaldehyde from a dynamical systems perspective. We find two mechanisms consisting of invariant phase space structures that may lead to identical molecular products. One of them is a slow passage via the flat region that fits the term frustrated dissociation used to describe roaming and is similar to the roaming mechanism in formaldehyde. The other mechanism is fast and avoids the flat region altogether. Trajectory simulations show that the fast mechanism is significantly more likely than roaming.