Optimization of ablation protocol for 200 nm UV femtosecond laser in precise U^|^ndash;Pb age dating coupled to multi-collector ICP mass spectrometry

Abstract

Copyright © 2011 by The Geochemical Society of Japan. (Horn and Gunther, 2003; Russo et al., 2004). Excimer laser (ExLA) or frequency multiplied Nd-YAG laser sources have been used for UV ablation. Ablation properties were improved as shorter wave-length laser systems such as, 266, 213, 193 (Guillong et al., 2003), and even 157 nm, were introduced (Telouk et al., 2003). As element fractionation was still an issue with these UV lasers (Guillong et al., 2003; Horn and Blanckenburg, 2007; Poitrasson et al., 2003), attention moved to the pulse duration of these lasers. An ultra short pulse laser was introduced with the infra-red (IR) fundamental wavelength (~800 nm) of Ti– sapphire fs laser. This system minimized elemental fractionation for most of the elements in silicate materials due to a reduction in the thermal fractionation effect at the ablation region (Claverie et al., 2009) and smaller particle sizes in the ablation aerosol (Koch et al., 2004). However, fractionation between elements with different physico-chemical properties still occurred. Frequency tripled (~266 nm) or quadrupled (~200 nm) UVFsLA beams have become available (Horn and Blanckenburg, 2007; Pisonero and Gunther, 2008), which theoretically should minimize element fractionation (Koch et al., 2004). Minimization of elemental fractionation, however, has only been achieved at the level of a few percent to ten percent drift during single hole ablation, or between difficult elements, such as U, Th, and Pb (Koch et al., 2006). Optimization of ablation protocol for 200 nm UV femtosecond laser in precise U–Pb age dating coupled to multi-collector ICP mass spectrometry