Broadband dielectric response of dichloromethane

A systematic study of the dielectric response of dichloromethane over a broad frequency range ( 8.5 ⩽ ν / GHz ⩽ 1000 ; ⩽ 4.3 THz at 25 °C) at temperatures from 5 to 35 °C is reported. The spectra are best described by a superposition of three contributions. The dominating loss peak at ∼ 70 GHz , fitted by a modified Debye equation accounting for inertial rise, represents the rotational diffusion of molecular dipoles. Additionally, two libration modes contribute, which are described by damped harmonic oscillators of resonance frequencies ∼ 0.9 THz and ∼ 2.1 THz . While the latter modes reflect the anisotropy of the dichloromethane molecule, the diffusive reorientation at long times appears to be rather isotropic.