1. a Carnegie Mellon University, Department of Chemistry , Pittsburgh , PA , U.S.A.
2. b Polymer Science & Eng. Dept. , University of Massachusetts , Amherst , MA , 01003
3. c TEH- Honggerberg (HPF) Institut fur Quantenelektronik, Laboratorium fur Nichtlineare Optik , CH , 8093 , Zurich