1. Physics Department and CENMAT, University of Trieste, via Valerio 2, I-34127 Trieste, Italy
2. IOM-CNR Laboratorio TASC, Area Science Park, S.S. 14 km 163.5, Trieste I-34149, Basovizza, Italy
3. Physics Department, University of Trieste, Strada Costiera 11, I-34151 Trieste, Italy
4. Department of Physics, Ningbo University, 818 Fenghua Road, Jiangbei District, 315211 Ningbo, People’s Republic of China
5. Elettra-Sincrotrone Trieste S.C.p.A., Area Science Park, S.S. 14 km 163.5, I-34149 Trieste, Italy
6. Institute of Theoretical Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
7. IOM-CNR DEMOCRITOS, Trieste, Italy and Italian Consortium on Materials Science and Technology (INSTM), Trieste, Italy