STEADY-STATE OPTICAL POLARIZATION ANISOTROPY OF RODLIKE MOLECULES UNDERGOING TORSIONAL TWISTING MOTIONS

An analytical expression was derived for the steady-state optical pola rization anisotropy expected for a rodlike molecule undergoing torsion al twisting motions about its long molecular axis. This expression is parameterized in terms of the ratio tau/Phi, where tau is the excited- state lifetime of the chromophore and Phi is a characteristic time for rotational twisting (Yoshimura et al., J. Mol. Biol. 179, 453-467, 19 84) that is proportional to the torsional rigidity of the flexible rod like molecule; the amplitude at any given value of tau/Phi is also det ermined by the angle between the chromophore transition dipole and the long molecular axis of the molecule.