1. School of Chemistry, Cantock’s Close, University of Bristol, Bristol BS8 1TS, United Kingdom
2. Centre for Nanoscience and Quantum Information, Bristol BS8 1FD, United Kingdom
3. HH Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
4. Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom
5. Bayer AG, Alfred Nobel Str. 50, 40789 Monheim, Germany