The infra-red absorption spectra of quartz and fused Silica from 1 to 7·5 μ II-Experimental results

Abstract

The accuracy of calibration, as already mentioned, was checked against CO 2 and water vapour bands. With the quartz prism the instrument could be set to show the 2·7 μ CO 2 bands resolved and within about 0·003μ of their known wave-lengths*; i. e., within 4 cm -1 . With the fluorite prism, resolution at 2·7 μ was inferior, but the structure of the water vapour band centred at 6·3 μ provided about 20 points for the checking of wave-lengths. Here the maximum discrepancy was 5 cm -1 and the mean discrepancy about 1·5 cm -1 , The wave-number error, therefore, is not libels to exceed 5 cm -1 in any part of the range investigated. The fraction of radiation transmitted by a specimen was measured to three figures and a mean of two or three observations at least taken for each wave-length setting. The accuracy varies from specimen to specimen and from point to point throughout the spectrum, depending on the magnitude of the galvanometer deflexions obtainable. The error is, however, nowhere likely to be greater than 0·01 and for much of the work is of the order of 0·002.