High-temperature Raman spectroscopic studies of indium halide vapors and molten salts: InX, InX2, InX3, and InAlX4 (X=Cl, Br)

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Abstract
Raman spectra were obtained at temperatures up to 1200 K for vapors over liquid indium halides with In:X (X=Cl, Br) ratios of 1:1, 1:2, and 1:3 and for vapors over liquid InAlX4. Spectra were also measured for molten InX2 and InAlX4 salts. The spectra of InX vapors consisted of O, Q, and S vibrational–rotational contours with maxima at ΔνQ(InCl) =305 cm−1 and ΔνQ(InBr) =213 cm−1. Pure rotational O and S band contours were also resolved at frequencies close to the frequency of the laser excitation line. Vibrational–rotational contours for the InX molecules were simulated using known molecular constants and accounting for contributions of both trace and anisotropic scattering. Preresonance enhancement of the Raman intensities and changes in the ’’linear’’ depolarization ratio with laser frequency were also observed for the InX molecules. The spectra of vapors over InX3 were characteristic of a dimer–monomer indium (III) halide equilibrium. Raman spectra of vapors over InX2 and InAlX4 liquids show the formation of vapor complexes and vapor dissociation according to the reactions: A comparison of the Raman spectra of liquid InX2 and InAlX4 with the corresponding spectra of the vapors indicates that the same molecular species are present in both phases.