1. British Petroleum Research Center, Chertsey Road, Sunbury-on-Thames, Middlesex, TW16 7LN (S.F.P., K.P.J. W.); Department of Chemistry, The University, Southampton, S09 5NH (P.J.H.); and Perkin-Elmer Limited, Post Office Lane, Beaconsfield, Bucks, HP9 1QA (A.J.T.), United Kingdom