Probabilities for Radiation and Predissociation. II. The Excited States of ch, cd, and CH⁺, and Some Astrophysical Implications

Decay rates determined from data on absolute phase shift versus frequency are presented for the A 2A, B 2 -, and 2 + states of CH, as well as for the B 2A state of CH+. The spectra were produced by electron-beam excitation of low-pressure CH4 and CD4 gases. Our results for the radiative lifetimes of the A and B states of CH support the recent findings of Fink and Welge. For the C +-X ll transition of CH and CD, the phase data are shown to represent quantitative measures of predissociation probabilities. Higber-resolution spectrograms are used to specify a simple model for the observed phase shifts in which the F1 spin components predissociate about 3 times faster than the F2 spin components. Since, as shown by our new data, nearly every photon absorbed in a line terminating in C + results in the photodestruction of CH, the formatinn rates of CH in interstellar space must be significantly increased to account for the observed intensities. It is also pointed out that the lack of agreement between calculations of the solar C-band intensity and equivalent-width measurements is not due to uncertainties in tbe molecular constants.