Dielectric response of polar liquids in the THz frequency range

Summary form only given. We use femtosecond THz time domain transmission spectroscopy to measure the complex dielectric constant of liquids in the THz frequency range and find, for all liquids studied that Debye-based models are inadequate in their description of the measured dielectric function because significant resonant absorption occurs throughout this frequency range. We show that our measured dielectric functions can be described by a model which combines resonant absorption with diffusive behavior, thus demonstrating for the first time that the nature of the dielectric constant is indeed changing from diffusive to oscillatory in character in the THz frequency range.