Ultrafast electron transfer measurement techniques

A state-of-the-art description of broadband ultrafast infrared pulse generation and multichannel CCD and IR focal plane detection methods has been given in this chapter. A few poignant examples of how these techniques can be used to extract molecular vibrational energy transfer rates, photochemical reaction and electron transfer mechanisms, and to control vibrational excitation in complex systems were also described. The author hopes that more advanced measurements of chemical, material, and biochemical systems will be made with higher time and spectral resolution using multichannel infrared detectors as they become available to the scientific research community. 

Ultrafast TRIR. The most fundamental processes of bond making, bond breaking and electron transfer have ultrafast dynamics. Access to these ultrafast time scales by TRIR requires a different approach from real-time measurements. Instead, pulsed-laser techniques based upon optical delay for measurement of time must be used. There are several approaches to measuring TRIR on the 10 — 10 s... 

The initial charge separation in PS I and PS II can be followed by what are known as ultrafast optical spectroscopy techniques. Several variations on this method exist, but they can be grouped into pump-probe absorbance difference and transient fluorescence methods (25, 26). In the first instance, the sample is irradiated with a pump pulse to initiate the electron transfer and the absorbance is measured using a probe pulse at a... 

Recent intensive investigations using pump-probe techniques and femtosecond anisotropy measurements have revealed that ultrafast energy transfer ( 80 fsec) from one of the two accessory bacteriochlorophyUs to the special pair and internal conversion ( 120 fsec) within the special pair occur prior to electron transfer from the special pair to one of the two bacteriopheophytins. 

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