Knowledge Bank

Fluorescence lifetimes have been determined for individual rotational levels near the predissociation limit in the $B2\Sigma +$ state of CH. The method is a measurement of relative quantum yields from laser-induced fluorescence intensities in a low pressure methane/oxygen flame. Levels studied are $N\prime =15$ to 17 in $\nu \prime =0,andN\prime =7$ and 8 in \nu^{\prime} = 1$. The collision free lifetimes decrease very quickly with increasing $N\prime$: for example, in $\nu \prime =0,\tau (N\prime =15)=150$ ns and $\tau (N\prime =17)\sim 1$ ns. Theoretical $calculations1$ agree well with these results. The competition between collisional, predissociative, and radiative processes has been studied for these peculiar rotational levels, and a model for state-specific rotational energy transfer has been tested in this electronic state.