文摘
Molecules are often born with high energy and large-amplitude vibrations. In solution, a newly formed molecule cools down by transferring energy to the surrounding solvent molecules. The progression of the molecular and solute鈥搒olvent cage structure during this fundamental process has been elusive, and spectroscopic data generally do not provide such structural information. Here, we use picosecond X-ray liquidography (solution scattering) to visualize time-dependent structural changes associated with the vibrational relaxation of Ib>2b> molecules in two different solvents, CClb>4b> and cyclohexane. The birth and vibrational relaxation of Ib>2b> molecules and the associated rearrangement of solvent molecules are mapped out in the form of a temporally varying interatomic distance distribution. The I鈥揑 distance increases up to 4 脜 and returns to the equilibrium distance (2.67 脜) in the ground state, and the first solvation cage expands by 1.5 脜 along the I鈥揑 axis and then shrinks back accompanying the structural change of the Ib>2b> molecule.