Knowledge Bank

Dispersed fluorescence spectra have been recorded pumping several $A~-X~$ electronic transition of $CCl2$. The analysis of the data yield well defined values for the harmonic and anharmonic constants for the symmetric ground state vibrations. Additional lines are observed at red shifts from $5000cm-1$ from the origin, which cannot be not assigned to any $X~$ vibrational levels. A possible explanation for these transitions would be perturbations of the singlet $A~$ by the low-lying triplet $a~$ state. This observation is in fair agreement with the theoretical predictions for the singlet-triplet state energy separation, and supports the new, alternative interpretations of the photodetachment spectrum of Lineberger et al.