Dielectric constants of H₂O and D₂O ice in the terahertz frequency regime over a wide temperature range

We measured the real and imaginary dielectric constants, ' and '', of H2O and D2O ice over the frequency range of 0.2–1.4 THz and temperature range of 20–240 K using terahertz-time domain spectroscopy and a gas-cooled cryostat. The constant ' increased with frequency; numerical calculations indicated a local maximum in ' at a few terahertz. The polarizability α obtained from ' exhibited a linear increase with respect to the temperature squared (T2). The constant '', which is mainly influenced by infrared phonon absorption, increased with the frequency and temperature over the entire range considered in this study. A mathematical model was created to describe the frequency and temperature dependence of ''.