1. Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
2. Jacobs Corporation, Hanover, Maryland 21076, United States
3. Optical Sciences Division, Code 5600, U.S. Naval Research Laboratory, Washington, District of Columbia 20375, United States
4. Center for Bio/Molecular Science and Engineering, Code 6900, U.S. Naval Research Laboratory, Washington, District of Columbia 20375, United States