1. Contribution from the Catalysts Department and the Aging and Reliability of Bulk Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185-1407, Departments of Chemistry, Colorado State University, Fort Collins, Colorado 80523, and University of California, Irvine, California 92717-2025, and Polymers and Coatings Group, MST-7, Los Alamos National Laboratory, Los Alamos, New Mexico 87545