The application of differential transmission spectroscopy in studying ultrafast phenomena

In this paper,the application of femtosecond spectroscopy in studying ultrafast phenomena is summarized first.Then,applications of differential transmission spectroscopy,one of important femtosecond spectroscopy,in studying ultrafast relaxation process are described in details,including the principle and experimental technique of detecting dynamics of excited states for isolated molecular system and the annihilation dynamics of excitons in crystals.Some examples are given.Finally,some problems met in studying ultrafast process by differential transmission spectroscopy and their solutions are discussed.