1. The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, Kraków 31-342, Poland, Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland, and Department of Chemistry, Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan