Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy

• DOI: 10.1038/s41467-021-27908-y
• Publication Date: 2022-01-11T11:02:51Z
• Authors: D. Mayer; F. Lever; D. Picconi; J. Metje; S. Alisauskas; F. Calegari; S. Düsterer; C. Ehlert; R. Feifel; M. Niebuhr; B. Manschwetus; M. Kuhlmann; T. Mazza; M. S. Robinson; R. J. Squibb; A. Trabattoni; M. Wallner; P. Saalfrank; T. J. A. Wolf; M. Gühr
• Keywords: Chemical Physics (physics.chem-ph); Science; ddc:530; Q; Institut für Physik und Astronomie; 500; FOS: Physical sciences; 01 natural sciences; 7. Clean energy; Article; 500 Naturwissenschaften und Mathematik; Physics - Chemical Physics; 0103 physical sciences; Institut für Chemie; info:eu-repo/classification/ddc/500

AbstractThe conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.