Investigating ultrafast internal conversion using extreme ultraviolet (XUV) time-resolved photoelectron spectroscopy

Alexie Boyer

IPCMS, Strasbourg

Mardi 3 juin à 11h –  Salle 0.17

In molecules, ultrafast processes triggered by the absorption of light are often facilitated by conical intersections (CIs) – molecular geometries where potential energy surfaces intersect. At these intersections, the Born-Oppenheimer approximation breaks down, and nuclear motion drives the transition between electronic states. These non-adiabatic transitions ultimately lead to the formation of photoproducts. In that case, the photo-induced dynamics is governed by several factors, including the topography of the potential energy surfaces and CIs, the presence of dark states, and the nuclear degrees of freedom responsible for electronic transitions. These factors influence both the speed and efficiency of photo-reactions. An accurate description of the non-adiabatic dynamics requires tracking the full evolution of the vibrational wavepacket created upon photoexcitation – from the initial Franck-Condon region to the formation of photoproducts.

In this context, the development of extreme ultraviolet (XUV) technologies has opened new opportunities to probe photo-induced dynamics. XUV time-resolved photoelectron spectroscopy (XUV-TRPES) was found to be a powerful technique for investigating ultrafast processes by monitoring the evolution of vibrational wavepackets along potential energy surfaces and through CIs. During this seminar, I will show several examples where XUV-TRPES was employed to investigate the ultrafast internal conversion of UV photoexcited molecules in both gas and liquid phases.