Observation of the Solvent Shell Reorganization around Photoexcited Atomic Solutes by Picosecond X-ray Absorption Spectroscopy

摘要

Solvation dynamics, the process of solvent shell reorganization upon electronic structure changes in a solute, is one of the most studied processes in chemical dynamics. This is based on its importance in liquid phase chemistry and in biology, where the solvent shell has an active role in assisting, hindering, or triggering chemical reactions. Solvation dynamics has been much studied using different ultrafast optical UV-vis and IR laser techniques since the 1980s, as well as by theoretical models and simulations. In the experimental studies, a short laser pulse excites a dye molecule in a solvent, inducing a sudden dipole moment change, to which the solvent molecules react by minimizing the free energy. This rearrangement is probed by recording, on the femtosecond time scale, the fluorescence, the excited-state absorption, or the stimulated emission of the dye molecule.