Chapter 5 Density Matrix Treatments of Ultrafast Radiationless Transitions

Abstract

In this chapter, the ultrafast radiationless transition processes are treated theoretically. The method employed is based on the density matrix method, and specifically, a generalized linear response theory is developed by applying the projection operator technique on the Liouville equation so that non-equilibrium cases can be handled properly. The ultrafast molecular processes are often monitored experimentally by transient spectroscopic techniques. In order to directly interpret these experimental observations, the susceptibility method is combined with the density matrix method so that linear/non-linear transient spectra of the system under consideration can be calculated. As an example, the interfacial photo-induced electron transfer process in dye-sensitized solar cell system, whose kinetics is often examined by the ultrafast spectroscopic techniques, is studied quantitatively with our methods.