1. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Solid State Physics Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece