The bending dynamics of acetylene

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Abstract
The dynamics and spectroscopy of (J=0) acetylene bending degrees of freedom are investigated using a reduced dimensional Hamiltonian. This Hamiltonian is obtained by applying an adiabatic approximation to average the vibrational Hamiltonian over the ground state in the three stretch coordinates. Within this approximation, an effective bend force field is obtained by adjusting force constants in the adiabatic potential to improve agreement between experimental and theoreticaleigenvalues. With minor modification, a global bend force field is determined that qualitatively describes the vinylidene vibrations and quantitatively describes the acetylene vibrations. This surface is compared to the results of a recent ab initio calculation. A dispersed fluorescencespectrum out of the excited à state, calculated from this model, is found to agree well with results of a recent experimental study.