Solvent effect on the vibrational dephasing of the ν2 (CN) and ν4 (CC) stretching modes in liquid acetonitrile and acetonitrile-d3 Original Research Article

The vibrational dynamics of CH3CN and CD3CN have been examined in pure substances and in mixtures with CCl4 at constant, room temperature, analysing the band shapes and the frequency shifts of ν2 (CN) and ν4 (CC) stretching modes. The effective temperature of the scattering volume, instead of the thermostatic value, was used to calculate and eliminate some secondary structures present in all the examined profiles. By doing this, it has been possible to correctly extract the dynamic parameters from the Raman isotropic profiles and from the relevant time correlation functions. The nonideality of the CH3CN/CCl4 mixture clearly emerges from the application of the Kubo theory in the frequency domain, following a calculation procedure previously developed in our laboratory. The concentration dependence of the bandwidths and the frequency shifts in ν2 mode have been interpreted within the theory of the local concentration fluctuation. Article Outline 1. Introduction 2. Experimental 3. Basic theory and data treatment 4. Results 4.1. CN stretching (ν2) 4.2. C–C stretching (ν4) 5. Discussion Acknowledgments Appendix A References