Abstract
Techniques are described whereby with the use of cylindrical lenses in conjunction with powerful grating spectrographs it has been possible to apply resolving power approximately one order of magnitude greater than is easily feasible with prism spectrographs for the photography of Raman spectra. Fine structures due to the isotopes of chlorine have been observed in the spectrum of carbon tetrachloride and chloroform. It is shown that the Δν = 217 cm−1 and Δν = 314 cm−1 frequency shifts of carbon tetrachloride are not resolvable even with these powerful spectrographs. The splitting of these lines into doublets by Langseth using very much smaller resolving power is not explainable in the light of our experiments. The “difference bands” arising from return transitions from the Fermi resonance doublet in the carbon tetrachloride spectrum have been found. These bands appear with approximately the intensity calculated by Horiuti. Fine structure of the totally symmetric frequency in the benzene spectrum has been measured under high dispersion. The results of these measurements are in good agreement with those of Langseth and Lord.
© 1946 Optical Society of America
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