Intensities in the Harmonic Band of Hydrogen Chloride

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Abstract
Measurement of absorption intensities.—The intensities of the first nine lines of the negative branch of the first harmonic absorption band of HCl at 1.76μ have been measured with a prism spectrograph, using a galvanometer and thermo-relay to observe thermopile voltages. The positive branch, not being resolvable, was measured as a whole. The areas under the lines in a plot of percent absorption against frequency were obtained for 5 different tube lengths, namely 74.5, 25.0, 14.96, 9.90 and 4.88 cm and the integrated absorption coefficient of each line was calculated from the slope of the curve of area against tube length at the origin by methods developed by Bourgin. The probable error of the intensity measurements for the stronger lines was 6 percent.