Acetonitrile (CH3CN) was adsorbed onto KBr, NaCl, NaBr, and KCl films. FTIR spectra were taken from 12 K to 160 K. From the obtained spectra, four peaks (3164, 2999, 2251, and 918 cm-1) were selected to be examined throughout the experiment. These peaks were monitored for changes in peak frequencies compared to the solid and gas phase literature values. Peak widths, heights, areas, and frequencies were examined for temperature dependent trends. The data were also used to explore both the desorption and vibrational dephasing behavior of CH3CN. From the four peaks, an E (2999 cm-1) and A1 (2251 cm-1) vibration were chosen to examine the orientational diffusion model. Orientational diffusion constants for both spinning (D||) and tumbling (D^) were calculated at each temperature. These values were then used to determine the activation enthalpy (DH*) and activation entropy (DS*). These values were reconstructed to see if the temperature dependent changes could be fit by the orientational diffusion model. It appears for CH3CN, the orientational diffusion model fit better for the tumbling diffusion constant D^ (E-type vibration) than it did for the spinning diffusion constant D|| (A1-type vibration).

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