1. Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland, Department of Chemistry, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, and Department of Chemistry, Rutgers, The State University of New Jersey, Newark, New Jersey 07102