[1] Bangor Univ, Sch Chem, Bangor LL57 2UW, Gwynedd, Wales
[2] STFC Rutherford Appleton Lab, Computat Sci & Engn Dept, Didcot OX11 0QX, Oxon, England
[3] STFC Rutherford Appleton Lab, ISIS Facil, Didcot OX11 0QX, Oxon, England
[4] Queen Mary Univ London, Sch Biol & Chem Sci, London E1 4NS, England