The Optical Band-Shape of a Vibronically Coupled Orbital Triplet

Having diagonalized the vibronic problem, a triply degenerate state coupled to a threefold vibration, we present calculated absorption and emission spectra for weak and moderate coupling strengths. The three peaked structure predicted by Toyozawa and Inoue appears at high temperatures and moderate coupling. However, some unexpected features (asymmetry of the structure, significant temperature dependence) also occur. The rotation-vibration coupling strengths in spherical top molecules having vibronically coupled triplet states are given.