Experimental measure of the planar itinerant oscillator

Abstract

The two-dimensional itinerant oscillator model for reorientational molecular motion in fluids has been reformulated recently to take account of inertial effects by Coffey et al. The new theory is here matched with experimental data from Rayleigh scattering in the depolarised mode (Litovitz et al.); original far infrared data on a highly dipolar species (CH₂Cl₂) in dilute solution and with molecular dynamics computations (of Tildesley and Streett et al.) using the atom–atom potential. In most cases studied experimentally and by molecular dynamical computation the angular velocity a.c.f. proves to be an oscillatory function of the time. This behaviour may be simulated closely by means of the present model. Furthermore, this short time oscillatory behaviour of the a.c.f. value appears to be a general feature of the reorientational motion of small molecules, even though the associated decay functions retain their familiar exponential forms at long times.