RE-EXAMINATION OF THE ELECTRONIC SPECTRUM OF HCP

Author Institution: Department of Chemistry, Princeton UniversityIn 1969, Johns et al published an extensive study of the electronic spectrum of HCP and DCP in the near UV. We are in the process of re-examining this spectrum using pulsed dye laser excitation and fluorescence detection in a pulsed jet apparatus. This work has demonstrated that their is an abrupt cut off of fluorescence near 41600 $cm^{-1}$, which we interpret as do to predissociation on the ground electronic surface. The spectrum shows a density of perturbations throughout the singlet systems that indicate substantial mixing with the still sparse $S_{0}$ levels. The spectrum in the region a few thousand wavenumbers below dissociation is very rich, with about 3 times the number of bands as a harmonic estimate of the total density of $S_{1}$ and $S_{2}$ vibrational levels. Most of the levels are unassigned, though it is clear that the origin of the ``C” state (now known to be $S_{2}$) is well below the earlier estimate. We plan Zeeman quantum beat measurements which we hope will aid in assignment."