1. Department of Physics; Harbin Institute of Technology; 92 West Dazhi Str. Harbin Heilongjiang 150001 P.R. China
2. Fuels and Energy Technology Institute; Curtin University; 1 Turner Avenue Perth WA 6102 Australia
3. Institute of Physical Chemistry; RWTH Aachen University; 2 Landoltweg 52056 Aachen Germany