Ultrasonic Absorption in Fused Silica at Low Temperatures and High Frequencies

The absorption of high‐frequency (60 kc. to 20 me. per second) sound waves in fused silica shows a large peak at low temperatures (30° to 50°K.). This absorption appears to result from some property of the glassy state since the absorption does not occur in crystalline silica. Data are presented showing the variation of rigidity and internal friction with temperature and frequency. It is shown that the source of the internal friction may be a structural relaxation. Some speculations are made on the nature of the structural relaxation and its relation to the glassy state.