Laser-Excitation of the Raman Spectra of Molten Salts

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Abstract
An apparatus is described for determining the Raman spectra of molten salts at temperatures up to ca. 1000°C, using a focused laser beam. The sample volume is 5 ml or less; a technique is described for filtering melts immediately before the spectral measurements. To demonstrate the performance of the apparatus, spectra were obtained for carbon tetrachloride (25°C), molten sodium nitrate (350°C), molten mercuric bromide (270°C), and molten sodium sulfate (900°C). Intensely red‐colored molten mercuric iodide was also characterized (it exhibits one polarized Raman band at 146 Δcm−1). For these tests, 6943 Å exciting radiation from a pulsed ruby laser was employed, but the apparatus can in principle be used with other lasers of different frequency. Comparison with spectra obtained using conventional mercury arc excitation shows that the laser compares favorably in the time needed to record spectra, and that spectra are more readily obtainable from high temperature melts and colored systems.