1. Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, Bruker Analytical X-ray Systems, Inc., 5465 East Cheryl Parkway, Madison, Wisconsin 53711-5373, Finnigan FT/MS Corporation, 6416 Schroeder Road, Madison, Wisconsin 53711, and Chemistry and Materials Science Divisions, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439