Far IR vibrational spectroscopic studies of the chemical dynamics of the pyridine/iodine system in solution

We have analysed the far infrared spectra of a mixture of pyridine and iodine in cyclohexane in such a way as to elucidate more clearly the role of the short time dynamicsof complex formation. We find that the so called ‘νD-I’ band at 90–120 cm−1 (depending on pyridine concentration) has its origins in the rapid spatial fluctuations between donor and acceptor. We detect experimentally the merging of vibrational and chemical reaction coordinates on the (sub ps) time scale of the experiment.