Origin of Ultrasonic Absorption in Heavy Water

Abstract

Hall's theory of structural relaxation is applied to explain the excess ultrasonic absorption in ${\mathrm{D}}_{2}$O. Two states, one characterized by higher volume and lower energy (icelike structure) and the other characterized by lower volume and higher energy (close-packed structure) are assumed to be available to each molecule of ${\mathrm{D}}_{2}$O. The occurrence of a density maximum ${\ensuremath{\rho}}_{max}$ at 11.2\ifmmode^\circ\else\textdegree\fi{}C and a static compressibility minimum ${\ensuremath{\beta}}_{0 min}$ at about 75\ifmmode^\circ\else\textdegree\fi{}C favors a two-state model for ${\mathrm{D}}_{2}$O. The absorption coefficient is calculated with three trial values of ${\ensuremath{\beta}}_{\ensuremath{\infty}}$ (16\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}12}$, 17\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}12}$, and 18\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{2}$/dyn). It is found that with ${\ensuremath{\beta}}_{\ensuremath{\infty}}=17\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ ${\mathrm{cm}}^{2}$/dyn, Hall's theory agrees very well with the experimental results.