Figure 1.

(left) The normalized electronic coupling autocorrelation function $C_{T_{DA}}^{\mathit{\text{norm}}}=\langle H_{DA}(t)H_{DA}(0)\rangle /\langle H_{DA}^2(0)\rangle$ in Ru-His 83 modified azurin decays on the time scale of tens of fsec,¹³ one order of magnitude longer than the Franck-Condon decay time.¹⁷ During each DA curve crossing event, the DA interaction is essentially unchanged. These fluctuations, rapid on the time scale of the ET rate, enter the rate through the mean squared coupling, $\langle H_{DA}^2\rangle$.