Plasma ignition thresholds in UV laser ablation plumes

• DOI: 10.1007/s003399900189
• Publication Date: 2008-08-21T21:49:13Z
• Authors: P. Clarke; P.E. Dyer; P.H. Key; H.V. Snelling
• Keywords: Ultraviolet; Laser Ablation; Pulse duration

Ultraviolet (UV) laser thresholds for plasma ignition on solid targets predicted from electron-neutral collisional heating are generally much higher than those observed experimentally. This inconsistency was reconciled by Rosen, et al. [2], who showed that excited-state photoionization played a key role in long-pulse UV laser breakdown. Here we develop a related model but with emphasis on pulses of ∼10 ns duration. Experimental results are also reported for titanium, copper, silicon, and ferulic acid targets in vacuum, irradiated with combinations of the XeF, KrF, and ArF lasers for comparison with predictions.