1. Department of Chemistry, Princeton University, Princeton, New Jersey 08544, Department of Mathematics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, Environmental and Occupational Health Sciences Institute, 170 Frelinghuysen Road, Piscataway, New Jersey 08854, and ATK Mission Research, 589 West Hollis Street, Suite 201, Nashua, New Hampshire 03062-1323