The dielectric properties of certain benzene derivatives in the solid state

The paper gives the results of an investigation of the dielectric properties of two chlorine-methyl substituted benzenes, pentachlortoluene and 1,2,4-trimethyl 3,5,6-trichlorbenzene, and of pentaiodobenzene, over the frequency range 50¿4.8×1010c/s, and discusses the observed behaviour in terms of modern dielectric theory. It was thought possible that these materials would exhibit resonance absorption owing to rotational molecular oscillation at the upper end of this frequency range. This phenomenon was not observed, but study of the dipolar absorption in the chlorine substituted compounds showed this to be characterized by a very narrow band of relaxation times, approximating closely to a single relaxation time. A quantitative estimate of the breadth of the relaxation time distribution was made. Directional permittivities of crystalline pentachlortoluene made at low frequency and at optical frequencies showed this material to be strongly anisotropic.