Vibrational Spectra of Molten Halides of Mercury. I. Mercuric Chloride, Mercuric Bromide, and Mercury Chlorobromide

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Abstract
The Raman spectra for HgCl2, HgBr2, and HgBrCl in the pure molten state are: HgCl2: 313 cm—1 (10, p), 376 (0, dp); HgBr2: 195 cm—1 (10, p), 271 (0, dp); HgBrCl: 111 (v.w.), 203 (v.w.), 236 (m), 319 (v.w.), and 335 (m). The vibrational assignment and force constants are reported in accord with the view that the linear X—Hg—X molecular species are retained in these melts as in the gaseous and crystalline states. The broad‐band shape for the intense Raman line in these melts and the appearance of a Raman forbidden frequency as a very weak line in the spectra of molten HgCl2 and HgBr2 are examined from the viewpoint of the nature of the Hg—X chemical bond and cooperative rotational interactions in these molecular molten salts. The appearance of the two Raman lines of HgCl2 and HgBr2 (319 and 203 cm—1) in the spectrum of HgBrCl is understood if a disproportion reaction is recognized in this mixed halide salt in the molten state.