An Interesting Infra-Red Absorption Band in Fused Quartz

Abstract

To check the calibration of an infra-red spectrometer, we attempted to locate a fairly sharp band of fused quartz reported by Dreisch¹ as existing at 2.75 with an intensity of absorption of 75 per cent when a 5 mm. specimen was used, and located by Parlin² at 2.71 with an intensity of absorption of 55 per cent in a 2 mm. specimen. To our surprise, no such band appeared, although we used several different plate and lens specimens, the thickest sample having a thickness of 5 mm. In the mean-time, a paper by Drummond³ has appeared, presenting a careful plotting of the spectra of crystalline and fused quartz. With 6 mm. samples of the latter, he found a 2.73 band with a 20 per cent absorption. His paper is particularly interesting because it plots for comparison the values of the absorption co-efficient K for fused quartz and for the ordinary and extraordinary rays of crystalline quartz. Throughout the 4–8 region, the graph for fused quartz assumes a kind of average position for the other two, which are qualitatively similar to each other. But in the 3 region there is a profound difference, a fact discovered by Dreisch¹, who ascribed it to a destruction of the crystal lattice upon fusion, the inference being that fusion shifts a 3 crystalline band to the new position.