We have performed photon correlation spectroscopy experiments to measure the lifetimes of density fluctuations in liquid salol in both the normal and supercooled regimes down to its glass transition at -55°C. Two modes were found to exist: a temperature-independent, hydrodynamic mode which we ascribed to entropy fluctuations and called the heat mode, and a strongly temperature-dependent, nonhydrodynamic mode due to internal, structural relaxations. We find that the internal relaxations suppress the heat mode when the heat-mode relaxation time is comparable to or less than the internal-mode relaxation time. This suppression occurs in the same temperature regime as a loss of power-law behavior for the viscosity as predicted by mode-coupling theory. We argue that the phenomena of the glass transition are a consequence of this suppression of the hydrodynamic heat mode by the internal relaxation mode as the temperature falls.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics