Molecular relaxation processes of 2-bromopropane in solutions from IR ν(C-Br) band shape analysis

The infrared (C-Br) stretching band profile of 2-bromopropane in pure liquid and in solution was studied. The frequency shifts, described by the Buckingham equation, account for the influence of the polarity and polarizability of the solvents. To evaluate the importance of the last term in the Buckingham equation, which describes the mutual influence of these two effects, a linear multidimensional regression analysis was done. The correlation factor increased when the cross term was considered. The concentration dependence of the FWHH (full width at half height) can be related to the vibrational relaxation processes, among them vibrational dephasing being the most important. More information about mechanisms responsible for the vibrational bandshape can be obtained from the correlation function Phi(t). As a result of modelling the experimental CF with Kubo-Rothschild's model, the modulation of the vibrational frequencies is found to be of intermediate type. (C) 1998 Elsevier Science B.V. All rights reserved.