THE COMPLEX SUSCEPTIBILITY OF A 2-POTENTIAL SYSTEM OF REORIENTATING POLAR-MOLECULES

The problem of accounting for the finiteness of collision times is elaborated from the viewpoint that the steady state law of motion of a dipolar particle is governed by two potentials. These describe the torque exerted on a given molecule by neighbouring particles. In liquids different classical laws of motion correspond to different potentials. We may consider that in a gaseous state one of the two potential functions U(curley theta) does not depend on the orientational angle of the rotor. In this case the usual quantum (equidistant) rotational spectrum of polar molecules results. Then the other potential, acting when gas particles are close one with another, may be introduced to describe classically the influence of collisions on the above discrete spectrum. The new approach employs fewer parameters of the molecular model than previously in the study of the two-potential state, since the number of particles in either state is expressed through lifetimes tau1, tau2 in the two states. Due to the mutual interference of the two potential states there occurs in a classical ensemble of molecules the sharpening of the frequency dependence of the absorption coefficient. The dielectric spectra at lower frequencies also change.