15min:

HUI-JU HSU, WEI-ZHONG CHANG AND BOR-CHEN CHANG, Department of Chemistry, National Central University, 300 Jung-Da Road, Chung-Li 32001, Taiwan.

New dispersed fluorescence spectra following the excitation of the CBr₂ ùB₁ X¹A₁ 2₀¹³ and 2₀¹⁴ bands at visible wavelengths in a discharge free jet expansion were acquired using an intensified charge-coupled device (ICCD) detector. The new dispersed fluorescence spectra show an improvement of the signal-to-noise ratios by a factor of roughly 10 with respect to our previous report. These new data extend the scan range from the maximum redshift of 2500 cm^-1 in our previous report^a to 6000 cm^-1 and reveal more details of the X¹A₁ state vibrational structure. Vibrational parameters including fundamental frequencies, anharmonicities, and coupling constants were determined for the CBr₂ X¹A₁ state. Moreover, additional vibrational structures, other than that of the singlet ground electronic state, starting at approximately 2725 cm^-1 were clearly observed in the new dispersed fluorescence spectra. Since these additional vibrational structures possibly belong to the background triplet state (ã³B₁), the singlet-triplet energy gap could be determined. Our progress on the experiments and analyses will be presented.