FTIR spectra of deuterated acetonitrile adsorbed onto KCl, KBr, NaCl, and NaBr films were taken from 12 K -160 K. Measurements of FWHM were made of selected A1 and E vibrations in an attempt to identify temperature-dependent trends. Changes in peak absorbance and frequency were monitored. Spectra of methyl fluoride and nitromethane were also examined. Increases in FWHM at increased temperatures were attributed to orientational diffusion. The parallel (D||) and perpendicular (D|) diffusion constants were calculated at each temperature and used to determine the activation enthalpy and activation entropy to orientational diffusion. The values of activation enthalpy and entropy were adjusted to determine if the observed temperature-dependent changes could be fit by the orientation diffusion model. It was determined that the model fit the CD3CN and CH3F data at mid and high temperatures. The CH3NO2 data could not be fit by the orientational diffusion model presumably since this molecule lacks C3v symmetry.
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