[1] Free Univ Berlin, Dept Phys, Arnimallee 14, D-14195 Berlin, Germany
[2] Max Planck Gesell, Fritz Haber Inst, Dept Phys Chem, Faradayweg 4-6, D-14195 Berlin, Germany
[3] DLR German Aerosp Ctr, Inst Opt Sensor Syst, Rutherfordstr 2, D-12489 Berlin, Germany
[4] Tech Univ Berlin, Inst Opt & Atom Phys, Str 17 Juni 135, D-10623 Berlin, Germany
[5] Helmholtz Zentrum Berlin Mat & Energie, Albert Einstein Str 15, D-12489 Berlin, Germany
[6] TeraSpinTec GmbH, Muhlenstr 12, D-14959 Trebbin, Germany