[1] Tech Univ Chemnitz, OSMP, D-09107 Chemnitz, Germany
[2] Tech Univ Chemnitz, Ctr Nanostruct Mat & Analyt, Chemnitz, Germany
[3] Univ Bayreuth, Bayreuth, Germany
[4] Stanford Univ, Dept Chem, Stanford, CA 94305 USA
[5] Leiden Univ, Huygens Lab, Leiden, Netherlands
[6] Univ Stuttgart, Inst Phys, D-7000 Stuttgart, Germany