Revisiting angular jump models of molecular reorientations in viscous liquids

We generalize the frequently used model of isotropic reorientational Browni an motion via small but finite angular steps to the case in which molecular reorientations by different angles take place around arbitrary axes. A sim ple approximation allows to give analytical expressions for experimentally relevant correlation functions, including spin lattice relaxation rates. We compare the results of our model to earlier treatments of rotational Brown ian motion. (C) 1999 American Institute of Physics. [S0021-9606(99)50227-4] .