Photochemical Reactions in Highly Excited States in Condensed Phase

Abstract

Properties of molecules are strongly dependent on their electronic states. Accordingly, we can expect different reactions of the molecule by selecting the electronic state through the change of the wavelength in the photoexcitation. Actually, reaction depending on the excitation wavelength has been reported for many molecules consisting of several atoms in the gas phase. Large molecules composed of ca.10 or more atoms, however, undergo the ultrafast intramolecular relaxation into the lowest excited state and the longitudinal relaxation of the vibrational excess energy follows this rapid conversion in the condensed phase. These fast relaxation processes have confined most of the photochemical processes to the reaction starting from the thermally equilibrated S₁ states. Reactions in higher excited states, however, have been recently reported for several molecules in the condensed phase. In the present article, we introduce these examples relating to isomerization and electron transfer reactions and discuss the prospect for future.