Munich, Germany, September 2, 2003. The heart of the Open University's New Wave Research UP193HE Excimer Laser Ablation System is the TuiLaser ExciStar M-100 excimer laser. The UP193HE is specifically designed for solid sample introduction to ICP, ICP-MS, noble gas MS and stable isotope MS instruments of all makes and models. Its high energy density (>35 J/cm2 at the sample), homogenized beam profile and short 193 nm wavelength make it ideal for opaque and highly transmissive materials alike.
TuiLaser has installed an ExciStar M excimer laser in a New Wave Research UP193HE laser ablation system at the Open University, Milton Keynes, United Kingdom. The ExciStar M from TuiLaser was selected due to its high operating efficiency and unique pre-ionising technology that delivers a beam that is already highly homogeneous before passing through the specially designed set of homogenizing optics. This configuration delivers a laser pulse to the sample which has unparalleled beam quality and significantly increased energy density. By integrating the ExciStar M, the extremely compact UP193HE system design is not affected.
The ExciStar M 193 nm excimer laser combined with the New Wave Research universal ablation platform was installed at the Open University in January, 2003 in conjunction with a Nu Instruments multi-collector ICP Mass Spectrometer for high precision isotope ratio measurements.
Dr. Peter Van Calsteren, Senior Research Fellow in the Department of Earth Sciences at the Open University said, "Our plasma ionisation mass spectrometer is an advanced, multi-collector research instrument. Its sensitivity is such that it should be possible, in certain circumstances, to measure 234U/238U and 230Th/232Th for uranium-series dating in situ using this laser ablation system. For example, a 2000-year-old authigenic carbonate (from a stalagmite or a coral) with 0.15 ppm uranium concentration contains approximately 1.2x1011 atoms of 230Th per gram. The weight of the material ablated in one pulse of 50 micron diameter is approximately 1.2x10-9 grams, so there are about 140 atoms of 230Th per pulse. The efficiency of the mass spectrometer is such that about 1 ion of 230Th per pulse is detected." Even under these circumstances where a total of only about 12 micrograms are ablated, it is possible to get results with 1% accuracy.
Excimer laser ablation is a powerful tool for entraining solid samples for mass and element fractionation. Dr. Van Calsteren continues, "At a wavelength of 193 nm the photon energy is absorbed by most materials in a sub-micron thick surface layer that ablates almost without thermal effect on the remaining material. The very high spatial resolution of this homogenized excimer system allows the study of incremental processes in the growth of individual minerals, or in the case of environmental archives such as stalagmites or shells, variations on an annual scale."
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