Orientational correlation times of nonrigid molecules. II. Tensor correlations

Second rank orientational correlation times of two and three bond chain molecules are calculated by means of a Mori formulation of the Fixman equations of motion of a stiff chain. The correlation times correspond to five tensor modes which sample the orverall tumbling of the asymmetric top molecules as well as the fluctuations in the torsional degree of freedom (for the three bond chain). Flexible three bond chains with 60° and 70° bond angle supplements have correlations times which satisfy an inequality τD<τ1<τ2, τR<τE where τD is associated with the tensor (b1−b2) (b1−b2), τ1 with b1b1, τ2 with b2b2, τR with the Rayleigh scattering mode b1b1+b2b2+b3b3, and τE with the tensor constructed from the end to end vector b1+b2+b3. The ratio of correlation times of first to second rank tensors is roughly 1–3 for the D mode, 3 for the E mode, and 3–5 for 1 and 2 modes.