Energy transfer dynamics, structures and intermolecular potentials of the glyoxal.argon complexes

Luc Lapierre, University of Pennsylvania


Using laser induced fluorescence (LIF) and stimulated emission pumping (SEP), we have characterized the Gl$\cdot$Ar and Gl$\cdot$Ar$\sb2$ complexes generated in a supersonic expansion. There are 3 isomeric structures of Gl$\cdot$Ar: Ar above the plane along the C$\sb2$ axis, and Ar in plane, either in the COH or HCCO gulf. The Ar shows large motion upon electronic excitation. In Gl$\cdot$Ar$\sb2$, the 2 Ar do not occupy single Ar position. Instead, they reside on the same side of the plane to allow Ar$\cdot$Ar interaction. Pair potential models can reproduce all isomeric structures. SEP was used to observe van der Waals (vdW) vibrational level in the electronic ground state. Normal mode analysis based on the pair potential model calculation is only partially successful for the vdW mode assignment. The component in a weakly bond van der Waals complex always undergo large amplitude motion with respect to each other even at zero point energies. These motions mimic collision with specific orientations, and may cause unique consequences in the dynamics of the component molecule. One example is provided by the glyoxal$\cdot$Ar complex, for which three different isomeric structures have been determined. It was observed that the different positions of Ar as well as the excitation of various van der Waals motions would induce dramatically different coupling between the glyoxal vibrations and the van der Waals motions, and affect the intersystem crossing rate of the glyoxal molecule.

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Recommended Citation

Lapierre, Luc, "Energy transfer dynamics, structures and intermolecular potentials of the glyoxal.argon complexes" (1991). Dissertations available from ProQuest. AAI9211959.