ENERGY-DISTRIBUTIONS IN THE LASER-ABLATION OF METALS AND POLYMERS

Time-of-flight (TOF) mass spectrometry has been used to investigate th e mass distribution of the material ablated from the interaction of a UV laser (FWHM = 30 ns, lambda = 308 nm) with aluminum, copper, and po lyimide at laser intensities of 3.8 x 10(12)-1.0 X 10(13) W m(-2). Hig h energy (10-152 eV) neutral particle emission was observed for all th ree materials. This is believed to be due to the formation of clusters in the laser-induced plasma which subsequently undergo rapid ionizati on (< 1 ps). The ions generated in the clusters are then subject to ex plosive expansion due to Coulomb repulsion and electron pressure. Mode ling of the cluster ionization process reveals that ions with energies > 100 eV can be produced by this process. (C) 1998 Elsevier Science B .V.