Solute dependence of three pulse photon echo peak shift measurements in methanol solution

Three pulse photon echo peak shift (3PEPS) measurement has recently become a popular method to study solvation and protein dynamics. In this paper, dependence of the 3PEPS signal on probe solute molecules was studied using several xanthene dyes and styryl dye molecules in methanol and compared with pump-probe measurements. For xanthene dyes, the decay was faster when the blue side of the absorption spectrum was excited. This effect is considered to be the result of a limited observation window and vibrational relaxation of the excess energy through higher density of states in the excited state. Nonlinear coupling may be also need to be considered. It seemed that the 3PEPS signal was more sensitive to excited state dynamics rather than to the ground state ones. For styryl dyes, a gradual increase of the peak shift was observed in the picosecond region, which may be the result of photoinduced isomerization.