1. Institute of Experimental Physics, University of Wrocław, Pl. Maxa Borna 9, 50-204 Wrocław, Poland
2. Institute of Physics, Odense University, Campusvej 55, 5230 Odense M, Denmark
3. Institute for Storage Ring Facilities, University of Aarhus, Bgning 520, Ny Munkegade, 8000 Aarhus C, Denmark
4. Department of Chemistry, University of Copenhagen, Universitetparken 5, 2100 Copenhagen, Denmark