Electronic transition moment and rotational transition probabilities in CH. I. A 2Δ–X 2Π system

Abstract

Vibrational band transition probabilities of the A–X electronic system of CH, v′=0, 1, and 2, have been measured in a low pressure flame using laser-induced fluorescence. These results improve earlier experiments that were complicated by energy transfer contributions, and expand measurements to very weak off-diagonal bands such as 0,2 and 1,3. The electronic transition moment derived from the vibrational branching ratio measurements differs slightly from ab initio calculations. Hönl–London factors using a mixed coupling scheme have been tested by experiment. Finally, a combination of these results with previously measured radiative lifetimes yields absolute absorption and emission coefficients for this system. A comparison between computed radiative lifetimes and collision-free experimental lifetimes suggests a predissociation rate in v′=0, N′≳17 of ∼1.5×105 s−1.