[1] LPC-ISMRA, boulevard du Maréchal Juin, 14050 Caen, France
[2] GANIL, boulevard Becquerel, 14076 Caen Cedex 5, France
[3] Fachbereich Physik, University of Rostock, 18055 Rostock, Germany
[4] Institute of Physics, Academy of Sciences, Cukrovarnická 10, 16200 Praha 6, Czech Republic