Isotopic dilution studies of the chloroform–chloroform‐ d system by Raman difference spectroscopy
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Raman difference spectroscopy has been used to measure small frequency shifts in the v1 and v2 bands of CHCl3 and CDCl3 in various mixtures of liquid chloroform and deuterochloroform. The frequency shifts relative to the pure liquids vary linearly with concentration, and at infinitive dilution are determined to be for CHCl 3: Δv1=+0.56 and Δv2=+1.92 cm -1; and for CDCl3: Δv1=+0.33 and Δv2=+1.82 cm-1. The fact that all frequency shifts are positive indicates that an exchange effect between like molecules is responsible for the phenomenon. The v4 bands show no frequency shifts but narrow substantially in bandwidth upon isotopic dilution. The position of the composite (CHCl3+CDCl3) v6 band relative to the pure liquids was also measured as a function of concentration. The data confirm that the frequency difference between this band in liquid CHCl 3 and in CDCl3 is 1.05 cm-1. The v6 frequency appear not to be significantly shifted by isotopic dilution. © 1980 American Institute of Physics.
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