EGAS41 - Swansea University

41 st EGAS CP 19 Gdańsk 2009
Recoil by Auger electrons: theory and application
Ph.V. Demekhin 1∗ , L.S. Cederbaum 2
1 Institut für Physik, Universität Kassel, D-34132, Kassel, Germany
2 Theoretische Chemie, PCI, Universität Heidelberg, D-69120 Heidelberg, Germany
∗ Corresponding author: demekhin@physik.uni-kassel.de
Translation-momentum coupling between electrons and nuclei in a molecule ejecting high
energetic photoelectrons may result in internal excitations of the molecule [1]. This effect
has been recently verified by observing photoelectron recoil-induced vibrational excitations
in molecules [2]. The study of recoil by high energetic photoelectrons increases the
experimental efforts, since photoionization cross sections typically fall off at high energies.
Alternatively, one can study the Auger decay after the K-shell photoionization, where the
photoelectron is only slightly above the 1s-threshold and the recoil momentum is provided
by the fast Auger electron.
The simple scheme to account for the momentum coupling between electrons and
nuclei suggested in [1] has been extended to describe the recoil of nuclei by a fast Auger
electron in diatomic molecules. The key for obtaining transparent equations is to represent
the occupied orbitals as a LCAO and the fast continuum electron by a plane wave. This
allows one to change the integration variables from the molecular frame to the laboratory
one in the analytical evaluation of the Coulomb integrals.
As an application, the impact of recoil by the fast Auger electron on the interatomic
Coulombic decay (ICD) following the K-LL Auger decay in the Ne dimer has been investigated
theoretically. ICD is a process where the transfer of relaxation energy from one
site of a weakly bonded complex leads to the emission of a low-energy electron from a
neighboring site [3]. The ICD after Auger decay in Ne 2 has been predicted theoretically
in [4] and was recently verified experimentally [5]. A detailed theoretical interpretation is
presented in [6].
The present computations are performed within the framework of the time dependent
theory of wave packet propagation. Our calculations illustrate an enormous effect of the
recoil of the nuclei on the computed wave packets propagating on the potential curve
populated by the Auger decay. The corresponding final state of the Auger process decays
further by ICD. We show that the recoil momentum imparted differently onto the nuclei
modifies the computed ICD spectra considerably.
References
[1] W.Domcke, L.Cederbaum, J.Electr.Spectr.Relat.Phenom. 13, 161 (1978)
[2] E. Kukk, K. Ueda, U. Hergenhahn, et al., Phys. Rev. Lett. 95, 133001 (2005)
[3] L.S. Cederbaum, J.Zobeley, F.Tarantelli, Phys. Rev. Lett. 79, 4778 (1997)
[4] R. Santra, L.S. Cederbaum, Phys. Rev. Lett. 90, 153401 (2003)
[5] K. Kreidi, T. Jahnke, T. Weber, et al., Phys. Rev. A 78, 043422 (2008)
[6] Ph.V.Demekhin, S.Scheit, S.D.Stoychev, et al., Phys.Rev.A 78, 043421 (2008)
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