[1] Univ Nova Lisboa, Lab Colisoes Atom & Mol, CEFITEC, Dept Fis,Fac Ciencias & Tecnol, Campus Caparica, P-2829516 Lisbon, Portugal
[2] Open Univ, Sch Phys Sci, Walton Hall, Milton Keynes MK7 6AA, Bucks, England
[3] CSIC, Inst Fis Fundamental, Serrano 113 Bis, Madrid 28006, Spain
[4] Univ Complutense Madrid, Dept Fis Atom Mol & Nucl, Ciudad Univ, E-28040 Madrid, Spain