1. Central Laser Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, United Kingdom (M.T., P.M., R.B., P.D.B., N.S., A.W.P.); School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom (D.C.G., J.D., J.A.W., M.W.G.); and Department of Chemistry, Imperial College, Exhibition Road, London, SW7 2AY, United Kingdom (W.M.K., C.M., D.P.)