NEW ELECTRONIC SPECTRA OF THE HCCI/DCCI $\tilde{A}-\tilde{X}$ VIBRONIC BANDS

Abstract

We have successfully acquired new dispersed fluorescence spectra following the excitation of several $\tilde{A} \leftarrow \tilde{X}$ vibronic bands of HCCl and DCCl at visible wavelengths in a discharge free jet expansion using an intensified charge-coupled device (ICCD) detector. The new dispersed fluorescence spectra reveal more details of the $\tilde{X}^{1} A^{\prime}$ state vibrational structure in these molecules than our previous $reports.^{a,b}$ Complete vibrational parameters including fundamental frequencies, anharmonicities, and coupling constants were determined for the HCCl/DCCl $\tilde{X}^{1} A^{\prime}$ state. Furthermore, perturbations from the background triplet state ($\tilde{a}^{3} A^{\prime \prime}$) were clearly observed in the new dispersed fluorescence spectra, and therefore the singlet-triplet energy gap could be determined. Additionally, a couple of new $\tilde{A} \leftarrow \tilde{X}$ vibronic bands were found in the laser excitation spectra of HCCl and DCCl. The rotationally resolved excitation spectra of a few $HC^{35}Cl \tilde{A} \leftarrow \tilde{X}$ vibronic bands and those of $HC^{37}Cl$ were recorded and analyzed. Our progress on the experiments and analyses will be presented.