Fig. 2.
(A) Transient absorption difference spectra at different delay times from 0.10 ps to 2.5 ps following ultrafast excitation (at 388 nm, and the pump pulse energy was 25 nJ per pulse) of a 25-mM solution of p-MeOPhOH with 25 mM added MQ+ in a 50-mM Tris buffer, pH = pD = 8.5, I = 0.8 M NaCl at T = 25 °C. (B) Absorption-time decay traces at λmax ∼ 560 nm corresponding to the decay of HMQ• by back electron transfer following pulsed excitation at 388 nm with 25 mM p-MeOPhOH and 25 mM MQ+ (blue) in H2O and D2O (black). Inset shows the traces magnified from ∼2.5–7.5 ps.