Electron transfer and energy

The dynamics of fast processes such as electron and energy transfers and vibrational and electronic deexcitations can be probed by using short-pulsed lasers. The experimental developments that have made possible the direct probing of molecular dissociation steps and other ultrafast processes in real time (in the femtosecond time range) have, in a few cases, been extended to the study of surface phenomena. For instance, two-photon photoemission has been used to study the dynamics of electrons at interfaces [ ]. Vibrational relaxation times have also been measured for a number of modes such as the 0-Fl stretching m silica and the C-0 stretching in carbon monoxide adsorbed on transition metals [ ]. Pump-probe laser experiments such as these are difficult, but the field is still in its infancy, and much is expected in this direction m the near fiitiire. 

Fig. 25. A cooperative closed trimer that exhibits intramolecular electron and energy transfer.

Sliwka HR, Melp TB, Foss BJ, Abdel-Hafez SH, Partali V, Nadolski G, Jackson H, and Lockwood SE. 2007. Electron- and energy-transfer properties of hydrophilic carotenoids. Chemistry—A European Journal 13(16) 4458 1466. 

The same research group extended their studies, proposing a systematic investigation of the core activities for different carbohydrate densities during biosensing processes.279 Three new mannosylated dendrimers with a Ru(bipy)3 core unit were synthesized, and the influence of the number and size of dendritic branches on the rate of electron and energy transfer, as well as the lectin-biosensing abilities (Scheme 41),... 

C. Various Forms of Electron and Energy Transfer Rate Constants... 

The events taking place in the RCs within the timescale of ps and sub-ps ranges usually involve vibrational relaxation, internal conversion, and photo-induced electron and energy transfers. It is important to note that in order to observe such ultrafast processes, ultrashort pulse laser spectroscopic techniques are often employed. In such cases, from the uncertainty principle AEAt Ti/2, one can see that a number of states can be coherently (or simultaneously) excited. In this case, the observed time-resolved spectra contain the information of the dynamics of both populations and coherences (or phases) of the system. Due to the dynamical contribution of coherences, the quantum beat is often observed in the fs time-resolved experiments. 

Equation (3.81) is similar to that in electron and energy transfer processes. 

Guldi DM, Hungerbuhler H, Asmus KD (1999) Inhibition of cluster phenomena in truly water soluble fullerene derivatives bimolecular electron and energy transfer processes. Journal of Physical Chemistry B 103 1444-1453. 

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