Rotational Raman spectra of a nearly symmetric rotor

Rotational Raman spectra for an accidentally or nearly symmetric rotor are discussed in detail. The spectral-moment theory is used to yield expressions for the polarizability invariants and for the different orientational correlation times involved. A generalization of Gordon'sJ-diffusion is presented which is able to reproduce also spectra in which the quantization of the rotational states is still present. A further generalization of the model is suggested to account for the molecular anisotropy during the collision process.