where x mj (ν mj ) and x nj (ν nj ) are harmonic-oscillator vibrational wavefunction factors, denoted in Ref. 87 as a vibrational factor. In the case where there is a single directly coupled final state and the vibrational factor is roughly unity, Robinson & Frosch note that even weak coupling will result in a rate constant of around 4 × 10 7 s -1 , agreeing qualitatively with experiment. Burland & Robinson calculate a rate of 3.24 × 10 1 s -1 for the B 2u →A 1g transition in benzene.