Affiliation: | (1) European Laboratory for Non-Linear Spectroscopy (LENS) and Department of Physics, University of Florence, and Istituto Nazionale di Fisica della Materia (INFM), L.go E. Fermi, 2, I-50125 Firenze, Italy (Fax: +39-55/224072, E-mail: MBELLINI@FI.INFN.IT), IT |