Transient nonlinear dielectric relaxation and dynamic Kerr effect from sudden changes of a strong dc electric field:: Polar and polarizable molecules

The nonlinear transient response of polar and polarizable particles (macromolecules) diluted in a nonpolar solvent to a sudden change both in magnitude and in direction of a strong external de field is considered. By averaging the underlying Langevin equation, the infinite hierarchy of differential-recurrence equations for ensemble averages of the spherical harmonics is derived for an assembly of polar and anisotropically polarizable molecules pertaining to the noninertial rotational Brownian motion. On solving this hierarchy, the relaxation functions and relaxation times appropriate to the transient dynamic Kerr effect and nonlinear dielectric relaxation are calculated. The calculations are accomplished using the matrix continued fraction method, which allows us to express exactly the solution of the infinite hierarchy of differential-recurrence relations for the first- and second-order transient responses of the ensemble averages of the spherical harmonics (relaxation functions). The results are then compared with available experimental data and solutions previously obtained for various particular cases. [S1063-651X(99)09808-6].