Solvent-solute interactions play a key role in solution-phase
chemistry. These interactions not only stabilize intermediate states by
solvation of the corresponding valence charge distributions, but modify
energy barriers thereby altering transition states, and allow for
ultrafast solvent dynamics in response to solute perturbations (e.g.
< 100 fs inertial responses of common solvents). Solvent-solute
interactions are thus often essential in determining ground-states and
steering chemical reactions in solution-phase chemistry.
We seek to understand the role of solvation and solvation dynamics
upon external perturbations through excitation of electronic and
vibrational degrees of freedom. While extended collective motions of
solvent molecules and their corresponding spectral density in the THz
spectral region are important for solvation dynamics, ultrafast local
probes of the solute are useful in understanding the influence of
solvation (dynamics) on the solute's constituents during chemical
Both, vibrational and core-level transitions extend over length
scales from functional groups to individual atoms, making them excellent
spectroscopic probes of solute-solvent interactions. While vibrational
transitions can largely be associated with structural dynamics,
core-level transitions report on valence electronic distributions as
well structural parameters such as bond lengths and geometries. We hope
to gain new insight into the role of solvent-solute interactions by
exciting collective solvent motions and employing a broad range of
spectral probes from meV to keV.