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

A method of evaluating the spectral moments M-2k(1) of the rotational corre lation functions for the first- and second-rank tensors of rigid asymmetric top molecules is developed. It is based on the calculation of the coeffici ents of a Taylor series expansion of the vector and tensor orientational co rrelation functions about t = 0 with the help of angular momentum theory, a nd is applicable to a pair intermolecular interaction potential with arbitr ary dependence on the angular variables. Equations for the second (M-2(l)), fourth (M-4(l)), and sixth (M-6(l)) spectral moments are obtained as a dem onstration of the ability of the method. The results for M-2(l) and M-4(l) coincide with previously known values and the equation for M-6(l) is new. A s particular cases, the theory contains the results for classical ensembles of symmetric tops, spherical tops, and linear molecules.