Measuring intramolecular charge transfer via coherent generation of THz radiation

We report the direct measurement of intramolecular electron transfer by detecting the electromagnetic (EM) waveform that is emitted during this process. It is detected in the time domain via free-spice electro-optic sampling and then related to the dynamics of the charge-transfer event. Electromagnetic Pulse generation from two systems, Betaine-30 in chloroform and DMANS in toluene, are studied to illustrate this technique. A finite-difference time-domain calculation with a time-dependent polarization is used to model the EM generation and propagation through the solution. This method is very general, since the movement of charge itself generates the EM waveform, and is sensitive to charge transfer occurring on a 0.1-10 ps time scale.