The dynamics of ions in a laser ablation plume from a number of metals irradiated by a ns-second pulse at 355 nm has been studied. The time-of-flight signals peak at flight times corresponding to velocities between 30 and 10 km/s with decreasing values for increasing atomic masses. The angular distributions of the integrated ion signals are strongly peaked in forward direction, and the values for the volatile Bi are somewhat higher than those for the other metals. The distributions have been analyzed on the basis of Anisimov's expansion model. The fraction of ionized atoms can be estimated from weight loss measurements and is about 0.5 for Ag and Al and 0.15 for Bi at a fluence of 2.5 J/cm(2). (C) 2002 Elsevier Science B.V. All rights reserved.
- Laser irradiation
- Plume expansion