Direct Measurements of Predissociation Probabilities in CH and CD Molecules

Quantitative measurements of nonradiative decay rates in the $C{}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ state of CH and CD molecules are presented via absolute phase shift versus frequency data and are interpreted as direct measures of predissociation probabilities. The $C$-state decay rates measured in CH are approximately three times larger than those in CD and comparison with absorption oscillator strength measurements shows that the predissociation probabilities of the rotational levels observed in CH range from approximately 3×${10}^7$ to 1.6×${10}^8$ ${\sec }^{-1\mathrm{}}$, i.e., approximately 3 to 18 times the radiative transition probability.