Effect of Temperature on the Intensity and Structure of Bands in the Infrared Spectrum of Rhombic Sulfur

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Abstract
The infrared spectrum of rhombic sulfur was obtained in the region between 750 and 2000 cm—1. The relative intensities of the bands at 845, 936, 1298, and 1513 cm—1 were measured as a function of temperature and sample orientation from —190° to 85°C. An expression is given that relates the temperature dependence for an overtone or combination band to the values of the component frequencies. The expression is used in conjunction with the measured temperature dependence to reject some previous assignments and to establish rough values of the component frequencies in the observed overtone and combination bands. A tentative assignment consistent with the rough values found for the component frequencies is made. In addition, the structure of a band is considered to be the result of combination with acoustic lattice modes, and the temperature dependence of the structure is analyzed from this point of view. The temperature dependence of the intensity of the structure of the band at 845 cm—1 far from the peak agrees roughly with the expression obtained, but the dependence close to the peak does not.