1. Advanced Materials Laboratory, Sandia National Laboratories, 1001 University Boulevard, SE, Albuquerque, New Mexico 87106, United States
2. Department of Chemistry, University of Hawaii─Manoa, 2545 McCarthy Mall, Honolulu, Hawaii 96822-2275, United States
3. Physics Department, Davidson College, 209 Ridge Rd., Davidson, North Carolina 28035, United States