Spectral moments of the rotational correlation functions for the first- and secondrank tensors of asymmetric top molecules

A method of evaluating the spectral moments M12k of the rotational correlation functions for the first- and second-rank tensors of rigid asymmetric top molecules is developed. It is based on the calculation of the coefficients of a Taylor series expansion of the vector and tensor orientational correlation functions about t = 0 with the help of angular momentum theory, and is applicable to a pair intermolecular interaction potential with arbitrary dependence on the angular variables. Equations for the second (Ml2), fourth (Ml4), and sixth (Ml6) spectral moments are obtained as a demonstration of the ability of the method. The results for Ml2 and Ml4 coincide with previously known values and the equation for Ml6 is new. As particular cases, the theory contains the results for classical ensembles of symmetric tops, spherical tops, and linear molecules.