Transition Moments, Franck—Condon Factors, and Lifetimes of Forbidden Transitions. Calculation of the Intensity of the Cameron System of CO

Abstract

The factors affecting the intensity of forbidden transitions in diatomic molecules are discussed. It is shown that using Franck—Condon factors to predict relative band intensities is less reliable for forbidden transitions than it is for allowed transitions. The intensity of the 0, 0 and 1, 0 bands of the a 3 Π− 1 Σ Cameron system of CO are calculated using perturbation theory. The intensity arises from spin—orbit mixing of the A 1Π state with the a 3Π state. From the known spin—orbit coupling constant of the a 1Π state and the known intensity of the fourth positive A 1 Π− 1 Σ transition, the oscillator strengths of the 0, 0 and 1, 0 bands are calculated to be 1.63×10 −7 and 1.99×10 −7 . Lifetimes of various rotational levels are shown to range from 2.9 to several hundred milliseconds.