Photochemical dynamics of Mg+-acetaldehyde: C-H vs. C-C bond activation pathways

We have investigated the chemical dynamics of Mg+-acetaldehyde bimolecular complexes following Mg+-centered (3p <-- 3s) excitation. Non-reactive disso ciation to Mg+ is the dominant decay channel. However, excitation in the 3p sigma (A ') <-- 3s sigma (A ') band also results in reactive dissociation to MgH+, MgCHO+, and MgCH3+ products, showing a clear sigma -like electroni c orbital alignment preference for chemical quenching. Isotope substitution shows reaction involves a direct attack on the aldehydic C-H or C-C bonds; the relative product branching indicates that the probabilities for C-H an d C-C bond cleavage are comparable. (C) 2001 Elsevier Science B.V. All righ ts reserved.