1. Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, U.K.
2. Department of Chemistry, University of Oxford, Chemistry Research Laboratory,
12 Mansfield Road, Oxford OX1 3TA, U.K.
3. Department of Physics, University of Oxford, Denys Wilkinson Building, Keble
Road, Oxford OX1 3RH, U.K.
4. Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry
Laboratory, South Parks Road, Oxford OX1 3QZ, U.K.