Aqueous solvation dynamics studied by photon echo spectroscopy

Abstract

Three-pulse photon echo peak shift measurements were employed to study aqueous solvation dynamics. A new perspective of dielectric continuum theory [X. Song and D. Chandler, J. Chem. Phys. 108, 2594 (1998)] aided in characterizing the system-bath interactions of eosin in water. Application of this theory provides solvation energies, which were used within the spectral density representation ρ(ω), to calculate the experimental peak shift. Simulations with only solvation contributions to ρ(ω), where a substantial amplitude of the solvation occurs within ∼30 fs, are remarkably consistent with our data. Furthermore, simulations using this theoretical solvation spectral density and an experimentally determined intramolecular spectral density yield an excellent total simulation of the peak shift data over the entire dynamic range. Our experimental results substantiate predictions that interaction-induced polarizability effects, contributing via a ∼180 cm−1 band in the spectral density, influence the initial dynamics.