Dresden 2003 – scientific programme
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MA: Magnetismus
MA 4: Kondo / Schwer-Fermionen / Quasi-Niedrigdimensionale Systeme (gemeinsam mit TT)
MA 4.10: Talk
Monday, March 24, 2003, 12:30–12:45, HSZ/405
On the nature of resonant photoemission — •Kai Starke2, Ashwani Kumar1, Massimo Tallarida1, Karsten Horn1, Günter Kaindl2, and Michael Martins3 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany — 2Fachbereich Physik, Freie Universität Berlin, Germany — 3DESY-Hasylab, Hamburg, Germany
For an electronic excitation process to be coherent it is mandatory that – as in a double-slit experiment – there are (at least) two possible excitation channels to reach the excited state. In particular, the excitation into discrete and continuum states gives rise to an asymmetric Beutler-Fano line shape of the excitation energy dependence. Although their appearance in tunneling spectroscopy of single atoms [1] and small clusters [2] on metal surfaces indicates a general applicability of Fano’s theory to coherent electronic excitations, there has been some confusion about the requirements for a ’truely’ resonant process to occur [3].
Using resonant photoemission at the Gd 4d → 4f photoexcitation threshold [4] as an example we show the existance of very different line asymmetries in the spectral region below the ’giant’ absorption edge. Our analysis using Cowan’s atomic multiplet code shows that there is substantial interference between excitation channels which have vastly different lifetimes of the intermediate state.
[1] N. Knorr et al., Phys. Rev. Lett. 88, 96804 (2002)
[2] T. Jamnela et al., Phys. Rev. Lett. 88, 256804 (2002)
[3] R. Mishra et al., Phys. Rev. Lett. 81, 1306 (1998)
[4] K. Starke, Magnetic Dichroism in Core-Level Photoemission, (Springer, Berlin, Heidelberg, 2000)