Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Particles and clusters
O 36.4: Vortrag
Mittwoch, 25. März 2009, 15:45–16:00, SCH A01
Initial-state effects in X-ray absorption spectra of sizeselected transition metal clusters — •Matthias Gramzow, Ralf Gehrke, and Karsten Reuter — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
X-ray absorption spectra (XAS) at the L2,3 edge of 3d transition metal solids are known to be sensitively affected by the created core hole. The recently reported experimental access to XAS of size-selected cationic transition metal clusters provides therefore a unique possibility to study the evolution of core hole screening from the atomic to the bulk-like limit [1]. While the measured data for the L2,3 branching ratio and the L3 absorption onset for cationic Ti, V and Co clusters containing up to 10 atoms shows indeed pronounced variations, it is unclear how much of this is simply due to the varying atomic coordination in the different isomer geometries (initial-state effects). As a first step towards a detailed interpretation of the experimental spectra we therefore use density-functional theory in conjunction with a basin-hopping sampling algorithm to identify the energetically lowest-lying isomers. On the basis of the obtained structures we disentangle the initial-state effects from the experimental data, and further quantify the amount of core hole screening using a Slater-Janak transition-state approach. [1] J.T. Lau et al., Phys. Rev. Lett. 101, 153401 (2008).