1. Department of Physics and Astronomy, University of Bologna, 40127 Bologna, Italy
2. Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, I-41125 Modena, Italy
3. Total Marketing and Services, Chemin du Canal BP 22, 69360 Solaize, France
4. University of Lille, CNRS, UMR 8516 - LASIRE - Laboratoire Avancé de Spectroscopie pour les Interactions, la Réactivité et l’Environnement, F-59000 Lille, France