1. Chemistry Department, Physics Department, and Environmental Sciences and Engineering Ph.D. Program, The University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, Departamento de Ingeniería Química, Universidad de Guanajuato, Col. N. Alta s/n, Guanajuato, Gto., 36050, and Department of Chemistry, University of Puerto Rico at Mayaguez, Mayaguez, Puerto Rico 00681