title: How a solute-pump∕solvent-probe spectroscopy can reveal structural dynamics: polarizability response spectra as a two-dimensional solvation spectroscopy.
abstract: The workhorse spectroscopy for studying liquid-state solvation dynamics, time-dependent fluorescence, provides a powerful, but strictly limited, perspective on the solvation process. It forces the evolution of the solute-solvent interaction energy to act as a proxy for what may be fairly involved changes in solvent structure. We suggest that an alternative, a recently demonstrated solute-pump∕solvent-probe experiment, can serve as a kind of two-dimensional solvation spectroscopy capable of separating out the structural and energetic aspects of solvation. We begin by showing that one can carry out practical, molecular-level, calculations of these spectra by means of a hybrid theory combining instantaneous-normal-mode ideas with molecular dynamics. Applying the resulting formalism to a model system displaying preferential solvation reveals that the solvent composition changes near the solute do indeed display slow dynamics similar to, but measurably different from, that of the solute-solvent interaction--and that this two-dimensional spectroscopy can effectively single out those local structural changes.
authors.affiliation: Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Sun
authors.forename: Richard M
authors.initials: RM
authors.lastname: Stratt