[1] Max-Planck-Inst. Physik Komplexer S., Nöthnitzer Straße 38, D-01187 Dresden, Germany
[2] Inst. High Perf. Comp. Data Bases, Fontanka 118, St. Petersburg 198005, Russia
[3] Department of Physics, St. Petersburg State University, Oulianovskaya 1, Petrodvorets, St. Petersburg 198904, Russia
[4] Fysik och Teknisk Fysik, Chalmers Tekniska Hogsk. och G., SE-412 96 Göteborg, Sweden
[5] Inst. für Theoretische Physik, TU Dresden, Mommsenstraße 13, D-01062 Dresden, Germany
[6] GSI, Postfach 11 05 52, D-64223 Darmstadt, Germany