1. CEMES-CNRS, 29 rue Marvig BP 94347, 31055 Toulouse Cedex 4, France, CUFR J. F. Champollion, Equipe Diagnostics des Plasmas Hors Equilibre, Place de Verdun 81012 Albi Cedex 9, France, Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong S.A.R., P.R. China, and National Synchrotron Radiation Research Center, Hsinchu, Taiwan