1. Department of Physical and Analytical Chemistry, Uppsala University, Box 259, SE-751 05, Uppsala, Sweden
2. Department of Photochemistry and Molecular Science, Uppsala University, Box 532, SE-751 20, Uppsala, Sweden
3. CEISAM, Université de Nantes, CNRS, 2 rue de la Houssinière, 44322 Nantes cedex 3, France