This paper focuses on the effect of pulse duration on ablation rate and behavior of plume in excimer laser ablation. Experimental results of laser ablation demonstrate that the 200 ns pulse laser exhibits a four to five times larger ablation rate than that with 20 ns pulse for the same laser fluence. CCD photography reveals that the plume velocity exceeds 4.5 km s(-1), corresponding to Mach 12. It is shown that these phenomena can be qualitatively explained by simulation results based on the molecular dynamics (MD) method. When the pulse duration becomes long, the number of ablated atoms increases accordingly under a constant laser fluence condition. The simulated results shows that the maximum velocity of expelled atoms ranges up to 20 km s(-1). (C) 1998 Elsevier Science S.A. All rights reserved. References: 3
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