1. Laboratory of Photomolecular Science; Institute of Chemical Sciences and Engineering; École Polytechnique Fédérale de Lausanne; 1015 Lausanne Switzerland
2. Benemérita Universidad Autónoma de Puebla.; CIDS, Av. San Claudio y 18 Sur, Col. San Manuel; Ciudad Universitaria, CP 72570; P.O. Box 1067 Puebla, Pue. 7200 México
3. Department of Chemistry; University of Cologne; Luxemburger Straße 116 50939 Cologne Germany
4. Laboratory for Photonics and Interfaces; Institute of Chemical Sciences and Engineering; École Polytechnique Fédérale de Lausanne; 1015 Lausanne Switzerland
5. Department of Engineering Sciences; Solid State Physics; Uppsala University; Box 534, SE 751 21 Uppsala Sweden
6. Current Address: Massachusetts Institute of Technology; Cambridge, MA USA 02139
7. Department of Chemistry- Ångström Laboratory; Uppsala University; 751 20 Uppsala Sweden