Measurement of small charge transfer optical absorption bands by modulation spectroscopy

Abstract

An optical modulation apparatus is described for the measurements of very weak (ε<1 M−1 cm−1) charge transfer optical absorption bands between electron donor–acceptor complexes. Such small bands, which are of interest in understanding the mechanism of electron transfer in physical, chemical, and biological systems, are undetectable by more traditional methods of optical spectroscopy due to their small size and their superposition on much larger background sample absorptions. An additional feature of the method is that the kinetics of the electron returning to its equilibrium state following photo-induced charge transfer can be measured.