The non-coincidence effect in N,N-dimethylformamide-CCl4 highly diluted binary mixtures. Experimental and theoretical results

We report results on the concentration dependence of the non-coincidence ef fect in the nu(C=O) mode in N,N-dimethylformamide-CCl4 mixtures. This study has been mainly addressed to the investigation of the experimentally obser ved sign inversion for this quantity in the low concentration range of chem ical mixtures, which is also reported in the literature. We argue that the sign inversion of the non-coincidence effect in N,N-dimethylformamide-CCl4 mixtures is an artefact originated by the presence of an intrinsic asymmetr y which with dilution moves from the blue to the red side of the band. The Logan theory for the thermodynamic state dependence of the non-coincidence effect in chemical mixtures offers a valuable tool for the interpretation o f the results in the whole concentration range. Different models are compar ed and discussed.