1. Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstr. 30, D-48149 Münster, Germany
2. Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box:
800-211, 201800 Shanghai, China
3. Instituto de Física São Carlos, Universidade de São Paulo, CP 369, São Carlos, São Paulo 13566-590, Brazil
4. Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 11635 Athens, Greece
5. Otto-Schott-Institut, Friedrich-Schiller-Universität Jena, Fraunhoferstr. 6, D-07743 Jena, Germany