1. Optical Science and Technology Center and the Department of Chemistry, 100 IATL, University of Iowa, Iowa City, Iowa 52242 (J.T.O., M.A.A.); and Fraunhofer-Institut fuer Angewandte Festkoerperphysik (IAF), Tullastrasse 72, D-79108, Freiburg, Germany (C.M., J.S., J.W.)