1. Contribution from the Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Canada K1N 6N5, Mitsui Norin Inc., 223 Miyabara, Fujieda City, Shizuoka Pref., 426-01 Japan, Max-Planck-Institut für Strahlenchemie, 34-36 Stiftstrasse, D-45470 Mülheim, Germany, and Techlogic Inc., 9404 Bac Place, Gaithersburg, Maryland 20877