Position- and time-resolved Stark broadening diagnostics of a non-thermal laser-induced plasma

Hao Liu, Benjamin S. Truscott, Michael N R Ashfold

Research output: Contribution to journalArticle (Academic Journal)peer-review

14 Citations (Scopus)


We present an analysis of the Stark-broadened line shapes of silicon ions in a laser-induced plasma using a model constructed, without assuming local thermodynamic equilibrium (LTE), using a Druyvesteyn electron energy distribution function (EEDF). The method is applied to temporally and spatially resolved measurements of Si2+ and Si3+ emissions from a transient plasma expanding into vacuum, produced by 1064 nm, nanosecond pulsed laser ablation of a Si (1 0 0) target. The best-fitting simulated line shapes and the corresponding electron number densities and temperatures (or equivalently, Druyvesteyn average energies) are compared with those returned assuming LTE (i.e. for a Maxwellian EEDF). Non-thermal behavior is found to dominate at all but the very earliest stages of expansion close to the target surface, consistent with McWhirter's criterion for the establishment of LTE. The Druyvesteyn EEDF always yields an equivalent or better model of the experimental measurements, and the observed increasingly strong departure from the Maxwellian case with time and distance from the ablation event highlights the essential invalidity of the LTE assumption for moderate-power, nanosecond laser-induced plasma expanding in vacuo.

Original languageEnglish
Article number015006
JournalPlasma Sources Science and Technology
Issue number1
Publication statusPublished - 10 Dec 2015


  • electron temperatures
  • laser-induced plasmas
  • non-LTE
  • optical emission spectroscopy
  • silicon
  • Stark broadening


Dive into the research topics of 'Position- and time-resolved Stark broadening diagnostics of a non-thermal laser-induced plasma'. Together they form a unique fingerprint.

Cite this