1. Department of Physics, Aberystwyth University, Aberystwyth SY23 3BZ, United Kingdom
2. Department of Physics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim, Norway
3. MAX IV Laboratory, Lund University, 221 00 Lund, Sweden
4. Department of Physics and Astronomy and Interdisciplinary Nanoscience Center, Aarhus University, Aarhus DK-8000, Denmark