Affiliation: | 1. Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universit?t Innsbruck, Austria, Fax: (+43) 603‐862‐2998;2. Current address: Department of Chemistry and Center of Nanotechnology, Kasetsart University, Bangkok 10900, Thailand;3. Permanent address: Department of Physics, University of New Hampshire, Durham, NH 03824, USA;4. Permanent address: Department of Experimental Physics, Comenius University, SK‐84248 Bratislava (Slovak Republic);5. Centre for Plasma Physics, Department of Physics and Astronomy, Queen's University Belfast, Belfast BT7 1NN, UK |