[1] Univ Warwick, Dept Chem, Gibbet Hill, Coventry CV4 7AL, W Midlands, England
[2] Univ Oxford, Dept Chem, Inorgan Chem Lab, South Parks Rd, Oxford OX1 3QR, England
[3] Univ Sci & Technol Beijing, Dept Phys Chem, Beijing 100083, Peoples R China
[4] DESY, Notkestr 85, D-22607 Hamburg, Germany