Tracking Temporal Development of Optical Thickness of Hydrogen Alpha Spectral Radiation in a Laser-Induced Plasma
1
Physics and Applied Physics Department, University of Massachusetts Lowell, Lowell, MA 01854, USA
2
Physics Department, University of Tennessee Space Institute, Tullahoma, TN 37388-9700, USA
*
Author to whom correspondence should be addressed.
Atoms 2019, 7(4), 101; https://doi.org/10.3390/atoms7040101
Received: 30 September 2019
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Revised: 23 October 2019
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Accepted: 23 October 2019
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Published: 4 November 2019
(This article belongs to the Special Issue Laser Plasma Spectroscopy Applications)
In this paper, we consider the temporal development of the optical density of the H spectral line in a hydrogen laser-induced plasma. This is achieved by using the so-called duplication method in which the spectral line is re-imaged onto itself and the ratio of the spectral line with it duplication is taken to its measurement without the duplication. We asses the temporal development of the self-absorption of the H line by tracking the decay of duplication ratio from its ideal value of 2. We show that when 20% loss is considered along the duplication optical path length, the ratio is 1.8 and decays to a value of 1.25 indicating an optically thin plasma grows in optical density to an optical depth of 1.16 by 400 ns in the plasma decay for plasma initiation conditions using Nd:YAG laser radiation at 120 mJ per pulse in a 1.11 Pa hydrogen/nitrogen gas mixture environment. We also go on to correct the H line profiles for the self-absorption impact using two methods. We show that a method in which the optical depth is directly calculated from the duplication ratio is equivalent to standard methods of self-absorption correction when only relative corrections to spectral emissions are needed.
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Keywords:
atomic spectroscopy; radiation transfer; hydrogen; laser-induced breakdown spectroscopy; stark broadening
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MDPI and ACS Style
Surmick, D.M.; Parigger, C.G. Tracking Temporal Development of Optical Thickness of Hydrogen Alpha Spectral Radiation in a Laser-Induced Plasma. Atoms 2019, 7, 101. https://doi.org/10.3390/atoms7040101
AMA Style
Surmick DM, Parigger CG. Tracking Temporal Development of Optical Thickness of Hydrogen Alpha Spectral Radiation in a Laser-Induced Plasma. Atoms. 2019; 7(4):101. https://doi.org/10.3390/atoms7040101
Chicago/Turabian StyleSurmick, David M., and Christian G. Parigger. 2019. "Tracking Temporal Development of Optical Thickness of Hydrogen Alpha Spectral Radiation in a Laser-Induced Plasma" Atoms 7, no. 4: 101. https://doi.org/10.3390/atoms7040101
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