Collison frequency

Troe and co-workers have also developed formulae for fwc- Again these depend on Bk and 5k as well as a third variable, the collision efficiency, /3c, which is a multiplicative factor applied to the collision frequency to account for weak collisions, i.e., the effective collison frequency is /3c< where (o is the actual collision frequency. 

D. Collison, M. Helliwell, V.M. Jones, F.E. Mabbs, E.J.L. Mclnnes, P.C. Riedi, G.M. Smith, R.G. Pritchard and W.I. Cross, Single and double quantum transitions in the multi-frequency continuous wave electron paramagnetic resonance (cwEPR) of three six-co-ordinate nickel(II) complexes ... 

Bondarev and Mardaeva were the first to observe that the Raman linewidth in mixtures could have an extra broadening, which reaches a maximum at intermediate concentrations (86). This broadening was attributed to fluctuations in the local concentration around the vibrator. This idea was elaborated theoretically by Knapp and Fisher (87). In a binary mixture of solvents, the first solvation shell of a vibration will have substantial fluctuations in composition. If the vibrational frequency is sensitive to the local composition, dephasing will result. Because it takes on the order of 10 ps for molecules to diffuse in and out of the first solvation shell, the frequency perturbations will last much longer than collisonal perturbations, and the resulting dephasing will be either in the slow modulation limit or in the intermediate range. 

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