Ultrafast Adsorbate Excitation Probed with Subpicosecond-Resolution X-Ray Absorption Spectroscopy
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Stockholm Univ. (Sweden)
- Chapman Univ., Orange, CA (United States)
- CNR-IOM, Trieste (Italy)
- Elettra-Sincrotrone Trieste (Italy)
- Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
- Stockholm Univ. (Sweden); SLAC National Accelerator Lab., Menlo Park, CA (United States)
- CNR-IOM, Trieste (Italy); Univ. of Trieste (Italy)
- SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States)
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. Finally, we suggest that coupling of the adsorbate to nonthermalized electron-hole pairs is responsible for the ultrafast initial excitation of the modes.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; Knut and Alice Wallenberg Foundation; Swedish Research Council (SRC); SIR; Helmholtz association
- Grant/Contract Number:
- 2016.0042; 2013-8823; AC02-76SF00515; AC02-05CH11231; VH-NG-1005; Nr RBSI14G7TL; CUP B82I15000910001
- OSTI ID:
- 1814461
- Journal Information:
- Physical Review Letters, Vol. 127, Issue 1; ISSN 0031-9007
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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