Using an ultrafast electronic-vibrational pulse-sequence, we show that the outcome of light-induced ET can be radically altered by mode-specific infrared (IR) excitation of vibrations which are coupled to the ET-pathway. IR-control is particularly challenging in condensed phase systems due to the ultrafast timescales involved, in particular rapid intramolecular vibrational redistribution. We demonstrate how an IR-pulse following UV-excitation perturbs nuclear-electronic (vibronic) interactions within a donor-bridge-acceptor system similar in design to those utilized in (bio)chemical light-harvesting, and alters charge-transport pathways and product state yields.
The results of nanosecond optical spectroscopy studies of hemoglobin geminate recombination on the 1-100 ns time scale are presented. Analysis of transient absorption data has shown that (i) the kinetics of O<SUB>2</SUB> recombination to hemoglobin cannot be described as a single-exponential process, and (ii) the predominant part of geminate recombination takes place on the initial stage of this process. The analysis pattern as two exponentials and background yields two processes occurring during the geminate recombination on the 1-100 ns time scale having the time constants of 1.2 +/- 0.2 ns and 16 +/- 2 ns. However, the signal-to-noise ratio of the data does not allow to make an unambiguous between several possible non-exponential decay models.