The Effect of Temperature on the Absorption Bands of Fused Quartz in the Infra-Red

The absorption bands of specimens of fused quartz, ranging in thickness from 2.0 mm for the 3μ region, to 4×${10}^{-4\mathrm{}}$ mm for the 8μ region, were studied. In regions where sufficient energy was available, an echelette grating was used to give greater dispersion. Measurements were taken at room temperature and at 850°C. In accord with previous work, the absorption band in the region of anomalous dispersion at 9μ was found to shift toward longer wave-lengths with increasing temperature. With higher resolution, however, fine structure bands were found which did not shift with the temperature, but did undergo marked changes in intensity. Several sharp bands between 2 and 4μ were found to remain fixed as the temperature was changed. A broad band which proved to be double, was found at 12.5μ. These bands did not shift with temperature. In most cases, there was a marked change in intensity with temperature. It was found that inside the strong bands, the absorption was much less at high temperatures, while outside the bands, the reverse was the case.