1. Stanford Synchrotron Radiation Laboratory, P.O.B. 20450, Stanford, California 94309, FYSIKUM, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, Materials Science and Engineering Department, University of California at Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720