1. Laboratory
of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, PO
Box 32, H-1518, Budapest 112, Hungary
2. Department
of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
3. Physics
Department and International Centre for Quantum and Molecular Structure, Shanghai University, Shanghai, 200444 China
4. Scuola Normale Superiore, Piazza
dei Cavalieri 7, I-56126 Pisa, Italy