ROTATIONAL STRUCTURE IN THE SINGLET-TRIPLET EXCITATION SPECTRA OF POLYATOMIC $MOLECULES.^{1}$

Abstract

$^{1}$ Work supported by NSF. $^{2}$ J. T. Hougen. Can. J. Phys. 42. 433 (1964).Author Institution: Department of Chemistry, Montana State University.; Physical Sciences. Inc., Research Park. Andover. MA 01810.; Department of Chemistry., University of Pittsburgh,We have observed rotational structure in the beam- and jet-cooled $T_{1}\leftarrow S_{0}$ phosphorescence excitation spectra of several molecules, including glyoxal, pyrazine and benzaldehyde. Each observed resolved or partially-resolved contour exhibits a significantly different shape, a shape that is also different from the corresponding bands in the $S_{1}\leftarrow S_{0}$ spectrum. We will discuss the origin of these differences in this talk. Our approach is that of $Hougen_{2}$ which emphasizes the strong connection between the radiative properties of the triplet state in the gas and condensed phase, in a natural way