1. Dipartimento di Chimica “G. Ciamician”, Università di Bologna, via Selmi 2, I-40126 Bologna, Italy
2. Departamento Quı́mica Fı́sica, Facultad de Ciencia y Tecnologı́a Universidad del Paı́s Vasco (UPV/EHU), Apartado 644, E-48080 Bilbao, Spain
3. Biofisika Institute, (CSIC, UPV/EHU), University of the Basque Country (UPV/EHU), Barrio Sarriena, S/N, 48940 Leioa, Spain
4. INAF - Osservatorio di Radioastronomia, via P. Gobetti, 101, I-40129 Bologna, Italy
5. Department of Physics, Stockholm University, Albanova University Center, SE-106 91 Stockholm, Sweden