1. Centrum voor Oppervlaktechemie en Katalyse, Departement Interfasechemie, K.U.Leuven, Kardinaal Mercierlaan 92, 3001 Leuven (Heverlee), Belgium
2. Department of Chemical Engineering, National Chung-Hsing University, Taichung 402, Taiwan, R.O.C.
3. Zettlemoyer Center for Surface Studies, Department of Chemical Engineering, Lehigh University, 7 Asa Drive, Bethlehem, Pennsylvania, 18015