1. Physikalisches Institut, Westfälische Wilhelms-Universität, Heisenbergstrasse
11, D-48149 Münster, Germany
2. Istituto di Scienze e Tecnologie Molecolari (ISTM), CNR, Via Golgi 19, I-20133
Milano, Italy
3. Polo Scientifico Tecnologico (PST), CNR, Via Fantoli 16/15, I-20138 Milano,
Italy