1. Department of Physics, Stanford University, Stanford, California 94305, USA
2. Scintillation Materials Research Center, Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
3. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
4. Department of Geological Sciences, Stanford University, Stanford, California 94305, USA