Abstract

The relative intensities of atomic emission lines have been analyzed in regard to a Boltzmann distribution of the electronic levels in the pulsed discharge. The analysis confirms a Boltzmann distribution with an excitation temperature of 3200 ± 220 K, a relatively low temperature compared with that for other excitation sources, such as microwave and radio-frequency discharges. The analysis also suggests that little ionization occurs via direct excitation in the discharge. The emission spectra from excited diatomic helium states have been analyzed and confirm the formation of He₂(<i>a</i>³&Sigma;_u⁺) and the Hopfield emission He₂(<i>A</i>¹&Sigma;_u⁺ → 2He(1¹<i>S</i>) continuum in the range 72 to 92 nm. Emission intensity-time profiles have been obtained for both atomic and diatomic helium emissions. Analysis of these profiles indicates that excited He₂ states are obtained by two reactions: (1) an excited atomic helium reacting with a ground-state helium atom, and (2) recombination of He₂⁺ with electrons. The study concludes that excitation in a discharge through helium at atmospheric pressure yields the following predominant species: He(2³S), He₂(<i>a</i>³&Sigma;_u⁺), Hopfield emission continuum 72-92 nm, and He₂⁺.

Spectroscopic Study of the Early Afterglow in Helium: Visible Bands and Hopfield Continuum*

Don Villarejo, Ronald R. Herm, and Mark G. Inghram
J. Opt. Soc. Am. 56(11) 1574-1584 (1966)

New Vacuum-Ultraviolet Emission Continua of Helium Produced in High-Pressure Discharges

R. E. Huffman, Y. Tanaka, and J. C. Larrabee
J. Opt. Soc. Am. 52(8) 851-857 (1962)

The Formation of Molecular Helium in a Glow Discharge*

W. D. Parkinson
J. Opt. Soc. Am. 41(9) 619-622 (1951)

Spectroscopic Study of the Early Helium Afterglow*

William S. Bickel and C. R. Burnett
J. Opt. Soc. Am. 55(11) 1504-1508 (1965)

Ar₂ excimer emission from a pulsed-discharge-excited pulsed supersonic gas jet

J. E. Tucker, M. F. Masters, B. L. Wexler, and S. K. Searles
Opt. Lett. 17(4) 288-290 (1992)