1. Institute for Physical Chemistry and Electrochemistry, Technical University of Dresden, 01062 Dresden, Germany
2. Institute for Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrücken, Germany
3. Present address: Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, 02015 HUT, Finland
4. On leave from: Department of Chemistry, Visva‐Bharati University, Santiniketan, India