Laser excited, dispersed fluorescence spectra have been recorded for a number of bands of the A ˜-X ẽlectronic transition of CCl 2 . Analysis of the data yields well defined values for the harmonic and anharmonic constants for the symmetric ground state vibrations. Additional lines are observed at red shifts !5000 cm À1 from the origin, which are not assignable in terms of the known X ~and A ˜state structure. A possible explanation for these transitions would be perturbations of the singlet X ~structure by the low-lying triplet a ˜state.

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Dispersed fluorescence spectra following excitation of the DCCl Ã-X̃ vibronic bands between 570 and 620 nm were successfully recorded for the first time using a combination of direct current discharge and supersonic free jet expansion techniques to produce the radical. This is the first experimental study on the DCCl X̃1A′ state vibrational structure. Analysis of the dispersed fluorescence spectra reveals details of the vibrational structure of the DCCl X̃1A′ state. Emission bands to all three vibrational modes were observed and the fundamental vibrational frequencies were determined: 2078 cm−1 (C–D stretch), 893 cm−1 (bend), and 801 cm−1 (C–Cl stretch). Vibrational parameters including anharmonicities and the bend-stretch coupling constant for the DCCl X̃1A′ state were also determined using a least-square fit. In addition, based on our results, the triplet-singlet energy gap (the zero-point level energy gap) could be estimated to be approximately 11±2 kcal/mol.