1. Contribution from the Department of Chemistry, University of Bergen, N-5007 Bergen, Norway, Physics Department, Western Michigan University, Kalamazoo, Michigan 49008, Advanced Light Source, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720, Keuka College, Keuka Park, New York 14478, Department of Chemistry, Portland State University, Portland, Oregon 97207-0751, and Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003