[1] Martin Luther Univ Halle Wittenberg, Inst Phys, D-06099 Halle, Germany
[2] Univ Lyon, Ecole Cent Lyon, Liris Lab, CNRS,UMR 5205, 36 Ave Guy Collongue, F-69134 Ecully, France
[3] Friedrich Schiller Univ Jena, Inst Festkorpertheorie & Opt, Max Wien Pl 1, D-07743 Jena, Germany
[4] European Theoret Spect Facil, Max Wien Pl 1, D-07743 Jena, Germany