On the symmetries of molecular reorientation processes in liquids

In this paper an irreducible expansion of the self and distinct part of the conditional pair distribution function G(ΩA, ΩB, t) is derived. For the description of several experiments which probe molecular reorientation processes it is of advantage not to require the self part of G(ΩA, ΩB, t) to be invariant under molecular symmetry operations. The orientational time correlation functions, however, as directly measurable quantities must possess this invariance. It is shown how the totally symmetrical structure of the orientational time correlation functions imposes certain symmetries on the time functions of the irreducible expansion of G(ΩA, ΩB, t).