Ultrafast Adsorbate Excitation Probed with Subpicosecond-Resolution X-Ray Absorption Spectroscopy

Elias Diesen*, Hsin Yi Wang, Simon Schreck, Matthew Weston, Hirohito Ogasawara, Jerry Larue, Fivos Perakis, Martina Dell'Angela, Flavio Capotondi, Luca Giannessi, Emanuele Pedersoli, Denys Naumenko, Ivaylo Nikolov, Lorenzo Raimondi, Carlo Spezzani, Martin Beye, Filippo Cavalca, Boyang Liu, Jörgen Gladh, Sergey KoroidovPiter S. Miedema, Roberto Costantini, Tony F. Heinz, Frank Abild-Pedersen, Johannes Voss, Alan C. Luntz, Anders Nilsson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We use a pump-probe scheme to measure the time evolution of the C K-edge x-ray absorption spectrum from CO/Ru(0001) after excitation by an ultrashort high-intensity optical laser pulse. Because of the short duration of the x-ray probe pulse and precise control of the pulse delay, the excitation-induced dynamics during the first picosecond after the pump can be resolved with unprecedented time resolution. By comparing with density functional theory spectrum calculations, we find high excitation of the internal stretch and frustrated rotation modes occurring within 200 fs of laser excitation, as well as thermalization of the system in the picosecond regime. The ∼100 fs initial excitation of these CO vibrational modes is not readily rationalized by traditional theories of nonadiabatic coupling of adsorbates to metal surfaces, e.g., electronic frictions based on first order electron-phonon coupling or transient population of adsorbate resonances. We suggest that coupling of the adsorbate to nonthermalized electron-hole pairs is responsible for the ultrafast initial excitation of the modes.

Original languageEnglish
Article number016802
JournalPhysical Review Letters
Volume127
Issue number1
DOIs
Publication statusPublished - 2 Jul 2021
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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