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arXiv:2512.13079

Unraveling real-time chemical shifts in the ultrafast regime

Daniel E. Rivas, Lorenzo Paoloni, Rebecca Boll, Alberto De Fanis, Ana Martínez Gutiérrez, Tommaso Mazza, Solène Oberli, Oliver Alexander, André Al-Haddad, Thomas M. Baumann, Christoph Bostedt, Simon Dold, Gianluca Geloni, Markus Ilchen, Dooshaye Moonshiram, Daniel Rolles, Artem Rudenko, Philipp Schmidt, Svitozar Serkez, Sergey Usenko, Ángel Martín Pendás, Michael Meyer, Jesús González-Vázquez, Antonio Picón

physics.chem-phphysics.opticsquant-phSubmitted Dec 15, 2025• Announced Dec 16, 2025
arXivHTMLPDF

Abstract

Traditional x-ray photoelectron spectroscopy (XPS) relies upon a direct mapping between the photoelectron binding energies and the local chemical environment, which is well-characterized by an electrostatic partial charges model for systems in equilibrium. However, the extension of this technique to out-of-equilibrium systems has been hampered by the lack of x-ray sources capable of accessing multiple atomic sites with high spectral and temporal resolution, as well as the lack of simple theoretical procedures to interpret the observed signals. In this work we employ multi-site XPS with a narrowband femtosecond x-ray probe to unravel different ultrafast dissociation processes of a polyatomic molecule, fluoromethane (CH$_{3}$F). We show that XPS can follow the cleavage of both the C-F and C-H bonds in real time, despite these channels lying close in binding energy. Additionally, we apply the partial charges model to describe these dynamics, and verify this extension with both advanced ab-initio calculations and experimental data. These results enable the application of this technique to out-of-equilibrium systems of higher complexity, by correlating real-time information from multiple atomic sites and interpreting the measurements through a viable theoretical modelling.

DOI
10.1103/y6dt-1sfw

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