Abstract
The dynamics of photolysis of glyoxal (HOC-COH) was investigated near the dissociation threshold on the triplet manifold through measurement of nascent fragment HCO in various internal states. Glyoxal serves as a prototypical molecule for both its three-body fragmentation and unimolecular reaction dynamics. Even when proteolysis energies lie below the threshold position on the triplet surface, minor production of nascent fragment HCO was observed. The results show that after photolysis near the threshold region on the triplet surface, HCO arising from the T 1 state appears to be a major component of products because the rotational levels of U state selected are gateway states with an enhanced rate of intersystem crossing.