Dielectric spectroscopy and molecular dynamics of methylene chloride CH 2Cl 2

Abstract

Precise measurements of the complex permittivity of methylene chloride (CH 2Cl 2) at 293 K have been made at frequencies in the range 50–310 GHz. These, when combined with earlier results, have made possible a determination of the complex permittivity over the entire zero to THz frequency region. These results show a distribution of dielectric relaxation times. The value of the Cole-Cole distribution parameter, α, was 0.03 and that of the relaxation time, τ, was 2.07 ps. A comparison of the power absorption, A(ω), spectra of pure methylene chloride with the normalized dilute solution spectra shows that: (a) the integrated absorption intensity of the pure liquid is 20% greater than that of its dilute solution, (b) the integrated absorption intensity for the dilute solution is higher than the value calculated, using Gordon's formula, by 46%, and (c) for frequencies greater than the the frequency, 0, of maximum power absorption, A(ω) falls off as ω −2 for dilute solutions whereas for the pure polar liquid the manner in which A(ω) falls off changes from being proportional to ω −2 to ω −4, for frequencies, = (ω/2π), well in excess of 0.