1. School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, U.K.; The Royal Institution of Great Britain, 21 Albemarle Street, London W1X 4BS, U.K.; School of Electronic and Electrical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.; and Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD, U.K.