1. Department of Chemistry, Durham University, Durham DH1 3LE, U.K., Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K., National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan, Center for Quantum Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531, Japan, Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198, Japan, and School of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, U.K.