1. Contribution from the Department of Physics, Washington State University, Richland, Washington 99352, W. R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, MS K8-88, P.O. Box 999, Richland, Washington 99352, Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112