Imaging Purely Nuclear Quantum Dynamics in Molecules by Combined X-ray and Electron Diffraction

Monitoring the motions of atoms and molecules inthecourseofchemicalprocessesisacentralgoaloffemtochemistry. Optical spectroscopic signals are usually sensitiveto electronic properties such as dipoles, polarizabilities, andelectronic charge densities rather than to nuclear motions. Inthis theoretical study, we propose a novel measurement that solelyand directly monitors the evolving nuclear wave packet and canthereby unambiguously image photochemical events in real time.We demonstrate how nuclear charge densities can be singled outby subtracting the ultrafast gas-phase X-ray and electron diffractionsignals in the photodissociation of thiophenol as it passes throughtwo conical intersections. This signal can reveal the shape and trajectory of the nuclear wave packets as well as the electroniccoherences in the vicinity of conical intersections.

Automated summary

In this theoretical study, a novel measurement is proposed to directly monitor the evolving nuclear wave packet and unambiguously image photochemical events in real time. By subtracting ultrafast gas-phase X-ray and electron diffraction signals, the nuclear charge densities can be singled out, revealing the shape and trajectory of the nuclear wave packets as well as the electronic coherences near conical intersections.