Institution: | (1) Department of Physics, Texas A & M University, 77843 College Station, Texas;(2) Max-Planck Institut für Quantenoptik, D-8046 Garching, Germany;(3) Center for Advanced Studies and Department of Physics and Astronomy, University of New Mexico, 87131 Albuquerque, New Mexico;(4) Present address: Institute of Theoretical Physics, Warsaw University, 00-681 Warsaw, Poland |