[1] Univ Paris 11, Phys Solides Lab, CNRS, UMR 8502, F-91405 Orsay, France
[2] CEA, Lab Leon Brillouin, CNRS, UMR 12, F-91191 Gif Sur Yvette, France
[3] Soleil Synchrotron, F-91191 Gif Sur Yvette, France
[4] Rutgers State Univ, Dept Chem & Chem Biol, Piscataway, NJ 08854 USA