XeF excimer laser ablation of metallic targets probed by energy-selective time-of-flight mass spectrometry

The kinetic energy distributions (KEDs) of ions produced during XeF laser a blation of metallic targets (Al and Cu) have been investigated by energy se lective time-of-flight mass spectrometry (ES-TOFMS). The observed Cu+ and A l+ emitted ions are characterised by a bimodal KED. The first peak is locat ed at very low kinetic energy (similar to 1 eV) and can be related to a the rmionic component; the second one is strongly dependent on laser fluence an d is due to energetic ions emitted from the laser produced plasma. In laser ablation of copper we observe only the thermal component at a laser fluenc e Lower than similar to 2.5 J cm(-2), whereas for aluminium targets the hig h kinetic part is always present. This feature has been analysed in terms o f the basic mechanisms involved in laser-vapour interaction and plume ionis ation. (C) 1999 Elsevier Science B.V. All rights reserved.