1. ISIS, Rutherford Appleton Laboratory, CCLRC, Chilton, Didcot, OXON, U.K., Unilever Research and Development Laboratory, Port Sunlight, Quarry Road East, Bebington, Wirral, U.K., Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, U.K., and Department of Applied Mathematics, Oxford University, Little Clarendon Street, Oxford, U.K.