A b initio methods (Hartree–Fock, generalized valence bond, and configuration interaction) have been used to characterize the electronic states of molecular analogs to trimethylaluminum. An understanding of the mechanism of photoexcitation and subsequent dissociation emerges as the calculations reveal that optical excitation results in a metastable bound state rather than a directly dissociative state. The substantial excess energy associated with the transition is stored in electronic and vibrational degrees of freedom other than those associated with the dissociation coordinate. This interpretation allows a large body of observations to be simply understood and has implications for the implementation of the technology of laser photolysis for thin-film deposition.