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Laser-Plasma and Self-Absorption Measurements with Applications to Analysis of Atomic and Molecular Stellar Astrophysics Spectra

1
Physics and Astronomy Department, University of Tennessee, University of Tennessee Space Institute, Center for Laser Applications, 411 B.H. Goethert Pkwy, Tullahoma, TN 37388, USA
2
Mathematics and Science Department, Fort Peck Community College, 605 Indian Avenue, Poplar, MT 59255, USA
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Atoms 2019, 7(3), 63; https://doi.org/10.3390/atoms7030063
Received: 28 May 2019 / Revised: 20 June 2019 / Accepted: 26 June 2019 / Published: 1 July 2019
(This article belongs to the Special Issue Atomic Processes in Plasmas: APiP-2019)
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Abstract

This work discusses laboratory measurements of atomic and diatomic molecular species in laser-plasma generated in gases. Noticeable self-absorption of the Balmer series hydrogen alpha line occurs for electron densities of the order of one tenth of standard ambient temperature and pressure density. Emission spectra of selected diatomic molecules in air or specific gaseous mixtures at or near atmospheric pressure reveal minimal plasma re-absorption. Abel inversion of the plasma in selected gases and gas mixtures confirm expansion dynamics that unravel regions of atomic and molecular species of different electron temperature and density. Time resolved spectroscopy diagnoses self-absorption of hydrogen alpha and hydrogen beta lines in ultra-high pure hydrogen gas. Radiation from a Nd:YAG laser device induces micro-plasma for pulse widths in the range of 6–14 ns, energies in the range of 100–800 mJ, and peak irradiances of the order 1–10 TW/cm 2 . Atomic line profiles yield electron density and temperature from fitting of line profiles to wavelength and sensitivity corrected spectral radiance data. Analysis of measured diatomic emission data yields excitation temperature of primarily molecular recombination spectra. Applications of the laboratory experiments extend to investigations of stellar astrophysics white dwarf spectra. View Full-Text
Keywords: atomic and molecular spectroscopy; time-resolved spectroscopy; laser plasma; laser-induced optical breakdown; stellar astrophysics spectra; white dwarf stars; hydrogen; carbon Swan spectra atomic and molecular spectroscopy; time-resolved spectroscopy; laser plasma; laser-induced optical breakdown; stellar astrophysics spectra; white dwarf stars; hydrogen; carbon Swan spectra
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Parigger, C.G.; Helstern, C.M.; Gautam, G. Laser-Plasma and Self-Absorption Measurements with Applications to Analysis of Atomic and Molecular Stellar Astrophysics Spectra. Atoms 2019, 7, 63.

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