Knowledge Bank

A naive pair potential model is used to calculate the intermolecular potential energy surface between glyoxal and argon. The glyoxal molecule is assumed to be composed of fragments (2 H and 2 CO) and the interaction potential is a sum of the individual pair wise potentials .$Ar\cdot H$ and $Ar\cdot CO$, which has been determined by previous molecular beam scattering $experiments.1$ The overall success of this model calculation in comparison with the experimental observations is surprisingly good: (1) The model accurately calculates the two isomeric structures of the glyoxal$\cdot$Ar complex, and the structure of the glyoxal$\cdot Ar2$ complex; (2) The calculated binding energies are consistent with the experimentally observed spectral shifts; (3) The model can account for the experimentally observed large structural change that occurs upon electronic excitation of glyoxal in one of the glyoxal$\cdot$Ar complex structures. A normal mode analysis of the van der Waals vibrational frequencies base on the model potential will also be discussed and compared to experimental results.