Time- and space-resolved optical Stark spectroscopy in the afterglow of laser-produced tin-droplet plasma

J. Scheers, R. Schupp, R. Meijer, W. Ubachs, R. Hoekstra, O. O. Versolato*

*Corresponding author voor dit werk

OnderzoeksoutputAcademicpeer review

6 Citaten (Scopus)
96 Downloads (Pure)

Samenvatting

The afterglow emission from Nd:YAG-laser-produced microdroplet-tin plasma is investigated, with a focus on analyzing Stark effect phenomena and the dynamical evolution of the plasma. Time- and space-resolved optical imaging spectroscopy is performed on 11 lines from Sn i-iv ions, in the 315-425-nm wavelength range. Stark shift-to-width ratios serve as the basis for unambiguous experimental tests of atomic physics theory predictions. Experiment and theory, where available, are found to be in poor agreement, and are in disagreement regarding the sign of the ratio in several cases. Spectroscopic measurements of the Stark widths in tandem with Saha-Boltzmann fits to Sn i and Sn ii lines, establish the evolution of the local temperature and density of the plasma afterglow, 20-40 ns after the end of the 15-ns-long temporally box-shaped laser pulse. A clear cool-down from ∼2 to 1 eV is observed of the plasma in this time window, having started at ∼30 eV when emitting extreme-ultraviolet (EUV) light. An exponential reduction of the density of the plasma from ∼1018-1017e- cm-3 is observed in this same time window. Our work is relevant for understanding the dynamics of the decaying, expanding plasma in state-of-the-art EUV nanolithography machines.

Originele taal-2English
Artikelnummer013204
Aantal pagina's9
TijdschriftPhysical Review E
Volume102
Nummer van het tijdschrift1
DOI's
StatusPublished - 9-jul.-2020

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