1. Institute for Nuclear Research, Pitesti, Campului Str., No. 1, P. O. Box 78, Postal Code 115400, Mioveni, Arges County, Romania
2. North Canton, OH 44721, USA
3. Lasers Atoms and Molecules Physics Laboratory, University of Science and Technology, Villeneuve d'Ascq, 59655, Lille, France
4. Physics Department, "Gheorghe Asachi" Technical University, Prof. Dr. Docent Dimitrie Mangeron Rd., No. 59A, 700050, Iasi, Romania