NONLINEAR ELECTROOPTICAL RESPONSE .2. STEADY-STATE DIELECTRIC-RELAXATION IN COUPLED FIELDS

Nonlinear dielectric response of polar and polarizable molecules disso lved in a nonpolar solvent arising from a weak ac field superimposed o n a strong de bias field are established. The general case when both p ermanent and induced dipole moments are taken into account is consider ed. By expanding the expectation value of the first Legendre polynomia l as a power series in the ac field strength up to the second order, w e find two distinct components in omega and 2 omega. Matrix continued fraction methods are used in order to express exactly the solution of the infinite hierarchy of the five-term differential recurrence relati ons for the ensemble averages of the Legendre polynomials (relaxation functions). The spectra of the real and imaginary parts of the first a nd second order complex dielectric response functions are presented in figures in order to show the essential differences between the linear and the nonlinear dielectric responses. The analytical expressions so obtained can be checked in so far as each component can be separated experimentally. (C) 1997 American Institute of Physics.