1. CEA, DSV, DRDC, Lab. Biochim. Biophys. Syst. Intégrés, CNRS, UMR 5092, F-38054 Grenoble, France, Brookhaven National Laboratory, National Synchrotron Light Source, Upton, New York 11973, and CEA, DRFMC, SCIB, LRM, UMR UJF-CEA 3, F-38054 Grenoble, France