1. Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99352, Chemistry, Umeå University, SE-901 87 Umeå, Sweden, Chemistry, George Washington University, 725 21st St., Washington, D.C. 20052, and Stanford Synchrotron Radiation Laboratory, 22575 Sand Hill Rd., Menlo Park, California 94025