DOI: 10.1063/5.0165693 ISSN:

Investigation of thermodynamic properties in picosecond laser-produced plasmas on silicon

Zelin Liu, Minsun Chen, Hanchang Huang, Shuai Hu, Chuan Guo, Hao Liu, Zhongjie Xu, Guomin Zhao, Weihong Hua, Kai Han
  • General Physics and Astronomy

The validity of local thermodynamic equilibrium (LTE) in plasma is a long-term concern for laser-induced breakdown spectroscopy applications. In this paper, the spatial and temporal dependence of LTE deviation in picosecond laser-induced plasmas has been proved. A picosecond (∼20 ps) laser operated at 532 nm was used to ablate a silicon target to produce plasma at a pressure of 10−5 mbar. A general electron energy distribution function was used to provide access to the insight into population ratios of different energy levels for the spatially and temporally resolved optical emission intensity of laser-induced plasma. A precise temporal and spatial LTE boundary of plasma generated in picosecond laser ablation was obtained, and the results showed that only at delay times of 180–300 ns, the plasma away from the surface (>4 mm) is in LTE.

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