1. The Center for Photoinduced Charge-Transfer and the Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, Xerox Corporation, 800 Phillips Road, 114-39D, Webster, New York 14580, the Department of Chemistry, Hendrix College, 1600 Washington Avenue, Conway, Arkansas 72032, and the Department of Chemistry, Wright State University, Dayton, Ohio 45435