1. Dipartimento di Chimica, Università di Siena, Via A. Moro 2, I-53100 Siena, Italy, Istituto per i Processi Chimico-Fisici del CNR, Via G. Moruzzi 1, I-56100 Pisa, Italy, Department of Chemistry, Grand Valley State University, Allendale, Michigan 49401, Max-Planck-Institut für Biophysikalische Chemie, D-37077 Göttingen, Germany, Department of Physics, Firat University, 23169 Elazig, Turkey, and Max-Planck-Institut für Dynamik und Selbstorganisation, D-37073 Göttingen, Germany