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Journal Article (Refereed)
January 2009

The effect of ambient pressure on laser-induced silicon plasma temperature, density and morphology

Cowpe, J & Pilkington, R & Hill, A E 2009, 'The effect of ambient pressure on laser-induced silicon plasma temperature, density and morphology', Journal of Physics D:Applied Physics, 42, pp.1-8.

Abstract

Laser-induced breakdown spectroscopy of silicon was performed using a nanosecond pulsed frequency doubled Nd : YAG (532 nm) laser. The temporal evolution of the laser ablation plumes was characterized under a range of low pressures. Electron densities were determined from the Stark broadening of the Si (I) 288.16 nm emission line and were found to be in the range 2.79 × 1016 cm−3 to 5.59 × 1019 cm−3. Excitation temperatures of 9000–21 000 K were calculated using the Si (I) 288.16 nm emission line to continuum ratio. The morphology of the laser plume, observed with respect to time, was seen to be strongly dependent on the ambient pressure. The density and temperature of the plasma were also found to vary critically with plasma morphology. Three ambient pressure regimes were identified where the plasma evolution was observed to differ markedly. Requirements for the existence of local thermal equilibrium conditions in the laser-induced plasmas are discussed with respect to these results.

Notes

 

We are the only group within the UK that is researching the fundamental aspects of LIBS This work describes for the first time an anomaly relating to the ambient pressure under which LIBS can be undertaken. It has been assumed that thermal equilibrium conditions exist within the laser induced plume, we have shown that this is not the case and that the morphology of the laser plume is strongly dependent on the ambient pressure.

Publication Details

Journal Name
Journal of Physics D:Applied Physics

Volume
42

Pagination
1-8.