1. LSI Irradiated Polymers Group (UMR 7642 CEA/CNRS/Ecole Polytechnique), CEA, IRAMIS, F-91128 Palaiseau Cedex, France, and SPCSI Chemistry of Surfaces and Interfaces Group and SPCSI Oxides Interfaces and Surfaces Group, CEA, IRAMIS, F-91191 Gif-sur-Yvette, France