Photodissociation dynamics of formaldehyde initiated at the T₁/S₀ minimum energy crossing configuration

B.C. Shepler, E. Epifanovsky, P. Zhang, J. Bowman, A.I. Krylov, and K. Morokuma
J. Phys. Chem. A 112, 13267 – 13270 (2008)

The photodissociation dynamics of formaldehyde is known to involve S₁, T₁, and S₀. Recent quasiclassical trajectory (QCT) calculations, in conjunction with experiment, have identified a 'roaming' H-atom pathway to the molecular products, H₂+CO [Townsend et al. Science 2004, 306, 1158]. These calculations were initiated at the global minimum (GM) of S₀, whih is where the initial wavefunction is located. The 'roaming' mechanism is not seen if trajectories are initiated from the molecular transition state saddle point (SP). In this Letter, we identify the minimum energy crossing configuration and energy of T₁S₀ potentials as a step towards studying the multi-surface nature of the photodissociation. QCT calculations are initiated at this configuration on a revised potentialenergy surface and the results are compared to those initiated, as previously, from the S₀ GM as well as the S₀ SP.

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