Measurement of Rotational Temperatures by Raman Spectroscopy: Application of Raman Spectroscopy to the Acquisition of Thermodynamic Values in a Chemical System
The standard expressions which describe the frequency positions and line strengths of the rotational Raman spectra of homonuclear diatomic gases in the rigid rotor approximation are presented. As the relative intensities of the rotational lines are related in a fairly simple manner to the thermal distribution of the gas molecules over the rotational states, it is shown how it is possible to obtain a value for the temperature of a gas by measuring its rotational spectrum.
Experimental results derived from a study of the pure rotational spectra of nitrogen and some of the practical problems encountered in their acquisition are discussed. A scanning double monochromator with photoelectric detection and paper chart output was used. The temperature could be measured to about ±½%.
At total pressures of about one atmosphere and room temperature, DC1 and Dimethyl-ether vapour form a small but significant amount of a gaseous hydrogen bonded compex Cl-D…O(CH3)2. The results of an experiment is reported in which the variation of trie equilibrium constant with temperature was followed by Raman spectroscopy. Thermodynamic values such as the enthalpy of complexation were thereby obtained. The temperatures of the system were measured by the Raman spectroscopic method outlined above, using nitrogen gas.
KeywordsRaman Spectroscopy Dimethyl Ether Rotational State Rotational Temperature Rotational Line
Unable to display preview. Download preview PDF.
- 1.G. Herzberg, Molecular Spectra and Molecular Structure I. Spectra of Diatomic Molecules, 2nd ed. (D. Van Nostrand Co., Inc., Princeton, 1950) p. 128.Google Scholar