Modelling the vibrationally mediated photo-dissociation of acetylene

A ten singlet state vibronic coupling Hamiltonian was constructed describing the seven internal coordinates of acetylene. A Σ symmetry-adapted polynomial expansion of the nuclear coordinates over diabatic elements was used to fit adiabatic energies obtained from ab initio calculations. The fitted vibronic Hamiltonian was subsequently used to model vibrationally mediated photo-dissociation (VMD) experiments. The model suggests that some control over dissociation channels might be achieved by choosing different ranges of pre-excitation and UV-excitation energies.