1. Department of Chemistry, University of Sheffield, Sheffield S3 7HF, U.K.
2. School of Chemistry, University of Nottingham, Nottingham NG7 2RD, U.K.
3. Central Laser Facility, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, STFC, Chilton, Oxfordshire OX11 0QX, U.K.
4. B. I. Stepanov Institute of Physics, Minsk, Belarus