THz Reflection Spectroscopy of H₂O(1) and D₂O(1)

Abstract

Using THz-spectroscopy we study the dielectric response of H₂O(1) and D₂O(1) between 0.1 and 2 THz from 270 to 363K. The response is modeled using a Debye model with a fast and slow decay time. Our results confirm that the temperature dependence of the slow decay time may be described by the recently reintroduced two-component model, with a critical point at 228K for H₂O and 235K for D₂O. As a consequence of this model, shifting the temperature scale for the slow relaxation time of D₂O by 7.2K, corresponding to the difference in temperature of maximum density, yields identical relaxation for D₂O and H₂O. This indicates a structural cause for the slow process.