Real-time tracking of the entangled pathways in the multichannel photodissociation of acetaldehyde.

The roaming mechanism, an unconventional reaction path, was discovered more than a decade ago in the studies of formaldehyde photodissociation, H2CO → H2 + CO. Since then, observations of roaming have been claimed in numerous photochemical processes. A closer examination of the presented data, however, revealed that evidence for roaming is not always unequivocal, and some of the conclusions could be misleading. We report here an in-depth, joint experimental and theoretical study of the title reaction. By tracking the time-evolution of the pair-correlated product state distributions, we decipher the competing, interwoven reaction pathways that lead to the radical (CH3 + HCO) and molecular (CH4 + CO) products. Possible roaming pathways are then elucidated and a more precise descriptor of the phenomenon is delineated.