1 Albert Einstein Center for Fundamental Physics (AEC), University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland; Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland.
2 Albert Einstein Center for Fundamental Physics (AEC), University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland; Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland. Electronic address: Saverio.Braccini@lhep.unibe.ch.
3 Department of Chemistry and Biochemistry (DCB), University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.
4 Albert Einstein Center for Fundamental Physics (AEC), University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland; Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland; Department of Physics "E. Pancini", University of Naples Federico II, Complesso Universitario di Monte S. Angelo, I-80126, Naples, Italy.
5 Albert Einstein Center for Fundamental Physics (AEC), University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland; Department of Chemistry and Biochemistry (DCB), University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland; Paul Scherrer Institut (PSI), Laboratory for Radiochemistry, CH-5232, Villigen, Switzerland.
6 Paul Scherrer Institut (PSI), Laboratory for Radiochemistry, CH-5232, Villigen, Switzerland.