1. Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
2. Department of Physics, Sophia University, Tokyo 102-8554, Japan
3. ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
4. Univ. Lille, UMR 8523 - Physique des Lasers Atomes et Molécules, F-59000 Lille, France
5. CNRS, UMR 8523, F-59000 Lille, France
6. Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain