Barrier crossing theory for ultra—fine detail in the far infra—red absorption of dipolar liquids

Abstract

Abstract The recent suggestion of ultra—fine detail in the far infrared power absorption of liquid acetonitrile (G.J.E.) is given support with a theory of rotational Brownian motion in cosine potential wells in the low friction limit . The theory and algorithm developed by Reid is used in this limit to produce a series of sharp absorptions in the far infrared as a function of well depth and multiplicity. With a multiplicity of 2 as many as eleven peaks are already observable which vary considerably in position and relative intensity with barrier height and temperature. The role of friction increasing is to broaden the individual peaks of the fine structure into a broad, continuous absorption profile - a “conventional” far infra—red power absorption profile [1,2]. The same model produces a broad dielectric loss curve at lower frequencies in accord with experimental observation (1.12 decades of frequency half—width). A preliminary investigation of the effect of an external electric field is made with the use, effectively, of a complex friction coefficient. Again the results appear to support the experimental observations of G.J.E. The theory provides strong evidence supporting an hypothesis [12] that the far infrared spectra of dipolar liquids are complex, composite profiles.