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Atomic fluorescence emitted from a corona discharge in helium above and below saturated vapour pressure

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journal contribution
posted on 12.06.2018, 13:10 by Nagham M. Shiltagh, Luis G. Mendoza Luna, Mark J. Watkins, Stuart C. Thornton, Klaus von Haeften
A new apparatus was constructed to investigate the visible and near infrared fluorescence spectroscopy of electronically excited helium over a wide range of pressures and temperatures, covering both the gaseous and liquid phases. To achieve sufficient throughput, increased sensitivity was established by employing a micro-discharge cell and a high performance lens system that allows for a large collection solid angle. With this set-up, several thousand spectra were recorded. The atomic 3s 1S → 2p 1P and 3s 3S → 2p 3P atomic transitions showed line shifts, spectral broadening and intensity changes that were dependent in magnitude on pressure, temperature and thermodynamic phase. While in the gas phase the lines showed little dependency on the discharge cell temperature, the opposite was observed for the liquid phase, suggesting that a significant number of atoms were solvated. Triplet lines were up to a factor of 50 times stronger in intensity than the singlet lines, depending on pressure. When taking the particle density into account, this effect was stronger in the gas phase than in the liquid phase of helium. This was attributed to the recombination of He2 +, He3 + and He4 + with electrons, which is facilitated in the gas phase because of the significantly higher mobility.

Funding

KvH acknowledges funding by the British Council (Alliance Programme). KvH is grateful for funding by The Leverhulme Trust (Res. Grant F00212AH), the Royal Society (Int. Exchange Grant IE130173), COST action CM 1405 (Molim). LGML acknowledges financial support from ERASMUS and the Mexican Consejo Nacional de Ciencia y Tecnolog´ıa (CONACYT) Scholarship No. 310668, ID 215334, NS acknowledges financial support Iraqi Minitry of Higher Education and Scientific Research (MoHESR) Scholarship No. 3312/2014- 1252. We thank N. Bonifaci, CNRS, Grenoble, for advice in the design and being introduced to corona discharges. We are indebted to the Space Research Centre at the University of Leicester who kindly lent us the Oxford Instr. closed cycle cryostat (M. Sims, D. Ross, J. Williams, J. Lapington, R. Limpenny).

History

Citation

The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics, 2018, 72 (5)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

The European Physical Journal D - Atomic

Publisher

EDP Sciences, Springer Verlag (Germany), Società Italiana di Fisica

issn

1434-6060

eissn

1434-6079

Copyright date

2018

Available date

12/06/2018

Publisher version

https://link.springer.com/article/10.1140/epjd/e2017-80322-4

Notes

Contribution to the Topical Issue “Dynamics of Molecular Systems (MOLEC 2016)”, edited by Alberto Garcia-Vela, Luis Banares and Maria Luisa Senent.

Language

en

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