Affiliation: | 1. Fakult?t für Chemie der Universit?t, Postfach 100131, 33501 Bielefeld, Germany, Fax: (+49)?521‐106‐6003;2. 1. Physikalisches Institut, Universit?t Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany;3. Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA;4. Institut Le Bel, Université Louis Pasteur, 4, Rue Blaise Pascal, 67070 Strasbourg, France |