EDP Sciences Journals List
Issue J. Phys. IV France
Volume 09, Number PR6, June 1999
International Conference on Coincidence Spectroscopy
Page(s) Pr6-127 - Pr6-132
DOI http://dx.doi.org/10.1051/jp4:1999629

International Conference on Coincidence Spectroscopy

J. Phys. IV France 09 (1999) Pr6-127-Pr6-132

DOI: 10.1051/jp4:1999629

Two electron photoemission processes in the valence band of solids

R. Herrmann, S. Samarin, H. Schwabe and J. Kirschner

Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Saale), Germany


Abstract
We present experimental evidence on photo double ionization processes in the valence band of solids. Applying a 'Time-of-Flight' electron spectroscopy technique, we measured the energy distribution of pairs of correlated electrons emitted from clean Cu(001)- and Ni(001)- crystals upon absorption of linearly polarized photons of 45eV energy. Data were taken for normal and grazing orientation of the light wave vector with respect to the crystal surfaces. The energy sharing distributions of electron pairs emitted from the vicinity of the Fermi-level show significant differences for Cu and Ni. For interpretation of our data, we consider a direct double ionization mechanism in competition with a two step process involving single photoexcitation and a subsequent collision of the photoelectron with an additional band electron. A theoretical approach by J. Berakdar including both mechanisms is in good agreement with our data. In this theory the differences between Cu and Ni are traced back to distinct relative contributions of both mechanisms in the two metals due to the different average electron density.



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