Direct observation of electron dynamics in the attosecond domain

Article metrics

Abstract

Dynamical processes are commonly investigated using laser pump–probe experiments, with a pump pulse exciting the system of interest and a second probe pulse tracking its temporal evolution as a function of the delay between the pulses1,2,3,4,5,6. Because the time resolution attainable in such experiments depends on the temporal definition of the laser pulses, pulse compression to 200 attoseconds (1 as = 10-18 s) is a promising recent development. These ultrafast pulses have been fully characterized7, and used to directly measure light waves8 and electronic relaxation in free atoms2,3,4. But attosecond pulses can only be realized in the extreme ultraviolet and X-ray regime; in contrast, the optical laser pulses typically used for experiments on complex systems last several femtoseconds (1 fs = 10-15 s)1,5,6. Here we monitor the dynamics of ultrafast electron transfer—a process important in photo- and electrochemistry and used in solid-state solar cells, molecular electronics and single-electron devices—on attosecond timescales using core-hole spectroscopy. We push the method, which uses the lifetime of a core electron hole as an internal reference clock for following dynamic processes9,10,11,12,13,14,15,16,17,18,19, into the attosecond regime by focusing on short-lived holes with initial and final states in the same electronic shell. This allows us to show that electron transfer from an adsorbed sulphur atom to a ruthenium surface proceeds in about 320 as.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Core-hole clock spectroscopy—schematic overview.
Figure 2: Core-hole clock spectroscopy—the spectroscopic signatures.
Figure 3: Quantitative charge transfer analysis of sulphur L1L2/3M1/2/3 Coster–Kronig autoionization spectra of c(4 × 2)S/Ru(0001) as a function of photon energy.
Figure 4: Theoretical charge transfer time for S in f.c.c. and h.c.p. hollow sites computed as S 3 p resonance lifetime.

References

  1. 1

    Zewail, A. H. Femtochemistry: atomic-scale dynamics of the chemical bond (adapted from the Nobel lecture). J. Phys. Chem. A 104, 5660–5694 (2000)

  2. 2

    Hentschel, M. et al. Attosecond metrology. Nature 414, 509–513 (2001)

  3. 3

    Drescher, M. et al. Time-resolved atomic inner-shell spectroscopy. Nature 419, 803–807 (2002)

  4. 4

    Baltuska, A. et al. Attosecond control of electronic processes by intense light fields. Nature 421, 611–625 (2003)

  5. 5

    Steinmeyer, G., Sutter, D. H., Gallmann, L., Matuschek, N. & Keller, U. Frontiers in ultrashort pulse generation: Pushing the limits in linear and nonlinear optics. Science 286, 1507–1512 (1999)

  6. 6

    Petek, H. & Ogawa, S. Femtosecond time-resolved two-photon photoemission studies of electron dynamics in metals. Prog. Surf. Sci. 56, 239–310 (1997)

  7. 7

    Kienberger, R. et al. Atomic transient recorder. Nature 427, 817–821 (2004)

  8. 8

    Goulielmakis, E. et al. Direct measurement of light waves. Science 305, 1267–1269 (2004)

  9. 9

    Björneholm, O., Nilsson, A., Sandell, A., Hernnäs, B. & Martensson, N. Determination of time scales for charge-transfer screening in physisorbed molecules. Phys. Rev. Lett. 68, 1892–1895 (1992)

  10. 10

    Ohno, M. Deexcitation processes in adsorbates. Phys. Rev. B 50, 2566–2575 (1994)

  11. 11

    Björneholm, O. et al. Femtosecond dissociation of core-excited HCl monitored by frequency detuning. Phys. Rev. Lett. 79, 3150–3153 (1997)

  12. 12

    Keller, C. et al. Ultrafast charge transfer times of chemisorbed species from Auger resonant Raman studies. Phys. Rev. Lett. 80, 1774–1777 (1998)

  13. 13

    Keller, C. et al. Femtosecond dynamics of adsorbate charge-transfer processes as probed by high-resolution core-level spectroscopy. Phys. Rev. B 57, 11951–11954 (1998)

  14. 14

    Feifel, R. et al. Observation of a continuum-continuum interference hole in ultrafast dissociating core-excited molecules. Phys. Rev. Lett. 85, 3133–3136 (2000)

  15. 15

    Wurth, W. & Menzel, D. Ultrafast electron dynamics at surfaces probed by resonant Auger spectroscopy. Chem. Phys. 251, 141–149 (2000)

  16. 16

    Brühwiler, P. A., Karis, O. & Mårtensson, N. Charge-transfer dynamics studied using resonant core spectroscopies. Rev. Mod. Phys. 74, 703–740 (2002)

  17. 17

    Schnadt, J. et al. Experimental evidence for sub-3-fs charge transfer from an aromatic adsorbate to a semiconductor. Nature 418, 620–623 (2002)

  18. 18

    Föhlisch, A. et al. Energy dependence of resonant charge transfer from adsorbates to metal substrates. Chem. Phys. 289, 107–115 (2003)

  19. 19

    Keller, C. et al. Electronic transfer processes studied at different time scales by selective resonant core hole excitation of adsorbed molecules. Appl. Phys. A 78, 125–129 (2004)

  20. 20

    Coville, M. & Thomas, T. D. Molecular effects on inner-shell lifetimes: Possible test of the one-center model of Auger decay. Phys. Rev. A 43, 6053–6056 (1991)

  21. 21

    Schwennicke, C., Jürgens, D., Held, G. & Pfnür, H. The structure of dense sulphur layers on Ru(0001) I. The c(2x4) structure. Surf. Sci. 316, 81–91 (1994)

  22. 22

    Jürgens, D., Schwennicke, C. & Pfnür, H. Surface structure analysis of the domain-wall phase of S/Ru(0001) using an efficient parameter optimization method. Surf. Sci. 381, 174–189 (1997)

  23. 23

    Krause, M. O. & Oliver, J. H. Natural widths of atomic K and L levels, K alpha X-ray lines and several KLL auger lines. J. Phys. Chem. Ref. Data 8, 329–338 (1979)

  24. 24

    Sánchez-Portal, D., Artacho, E., Ordejón, P. & Soler, J. M. Density-functional method for very large systems with LCAO basis sets. Int. J. Quant. Chem. 65, 453–461 (1997)

  25. 25

    Soler, J. M. et al. The SIESTA method for ab initio order-N materials simulation. J. Phys. Condens. Matter 14, 2745–2779 (2002)

  26. 26

    Borisov, A. G., Kazansky, A. K. & Gauyacq, J. P. Resonant charge transfer in ion–metal surface collisions: Effect of a projected band gap in the H-Cu(111) system. Phys. Rev. B 59, 10935–10949 (1999)

Download references

Acknowledgements

We acknowledge support by the staff of MAX-lab, Lund, Sweden, in particular J. N. Andersen and the ARI program. This work was supported by the Deutsche Forschungsgemeinschaft under Schwerpunktprogramm 1093 “Dynamik von Elektronentransferprozessen an Grenzflächen”, the Basque Departamento de Educación, the University of the Basque Country, the Spanish MEC, European Network of Excellence NANOQUANTA, and Max-Planck Awards for Scientific Cooperation to P.M.E. and D.M.

Author information

Correspondence to W. Wurth.

Ethics declarations

Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.