1. Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P. O. Box 9502, 2300 RA Leiden, The Netherlands, Fax: +31‐715274671
2. Université Bordeaux 1, CNRS‐CRPP, 115 avenue du Dr. A. Schweitzer, 33600 Pessac, France
3. ALS, Berkeley Lab, 1 Cyclotron Road, MS2‐400, Berkeley, CA 94720, USA