1. Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3000, Bern 9, Switzerland
2. Institut Laue-Langevin, BP156, 38042 Grenoble, Cedex 9, France
3. Polish Academy of Sciences, Institute of Molecular Physics, Smoluchowskiego 17, 60-179 Poznan, Poland
4. Department of Chemistry, School of Molecular and Microbial Sciences, The University of Queensland, Brisbane, Queensland, Australia, 4072