Collective behavior of supercooled liquids in porous media

The macroscopic behavior of a restricted liquid has been studied through ultrasonic velocity and attenuation measurements utilizing a picosecond colliding-pulse optical technique. Transparent porous sol-gel glasses allowed a study of the collective fluid dynamics as a function of confining pore radius and temperature. The acoustic response of the supercooled state was found to be strikingly different from that of any ordinary liquid, and consistent with a simple model. © 1988 The American Physical Society.