1. Centre for Materials Science and Nanotechnology Department of Chemistry University of Oslo Gaustadalléen 21 Oslo NO‐0349 Norway
2. Centre for Materials Science and Nanotechnology Department of Physics University of Oslo P. O. Box 1048 Blindern Oslo NO‐0316 Norway
3. Department of Chemical and Process Engineering University of Strathclyde 75 Montrose St Glasgow G1 1XJ UK