Light scattering spectroscopy of the liquid-glass transition

Supercooled liquids approaching the liquid-glass transition exhibit unusual properties associated with structural relaxation. The mode-coupling theory (MCT) of supercooled liquid dynamics shows that non-linear interactions among density fluctuation modes can produce effects resembling these observations. MCT produces detailed predictions for the dynamics of density fluctuations in supercooled liquids, including a crossover from liquid to glassy dynamics at a critical temperature T_c. Recent light scattering studies of supercooled CaKNO₃ are described that have provided detailed tests of MCT both above and below T_c, including a cusp in the scaling time at T_c=105+or-5 degrees C. These experiments are reviewed, and comparisons with both the idealized and extended versions of MCT are described.