1. Physics Department, Syracuse University, Syracuse, New York 13244, Universitá di Catania, DMFCI, 95125 Catania, Sicily, Italy, NASA Ames, Mail Stop 245-6, Moffett Field, California 94035, Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel, Faculty of Physics, Weizmann Institute of Science, Rehovot 76100, Israel, and INAF-Osservatorio Astronomico di Capodimonte, Napoli, Italy