Experimental investigation of plasma-broadened hydrogen Balmer lines at low electron densities

Journal Article · Tue Jan 01 04:00:00 EST 1980 · Phys. Rev., A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.21.319· OSTI ID:5753406

Ehrich, H; Kelleher, D E

The central regions of the plasma-broadened Balmer lines H/sub ..cap alpha../, H/sub ..beta../, and H/sub ..gamma../ have been measured in a wall-stabilized arc over an electron density range between approximately 4 x 10/sup 14/ and 2 x 10/sup 16/ cm/sup -3/. The experimental profiles exhibit much less structure in the line core than predicted by theories based on the static-ion approximations. These discrepancies increase towards lower electron densities and lower Balmer-series members, e.g., the H/sub ..cap alpha../ half-width as well as the central minimum of H/sub ..beta../ deviate by about a factor of three from current hydrogen-broadening theories at low electron densities (10/sup 15/ cm/sup -3/). Consistent with earlier experiments, the central minimum of H/sub ..beta../ was found to depend on the reduced mass of the radiator-ion perturber system. Also, the temperature dependence of the experimental data suggests that the central H/sub ..beta../ minimum depends approximately linearly on the relative mean velocity between radiator and perturber. Extrapolation of the H/sub ..beta../ results to the static case yields good agreement with the quasistatic calculations. The theoretically predicted ''shoulder'' in the H/sub ..gamma../ line shape is nearly absent in the experimental profile. Besides ion dynamics, fine-structure (spin) effects can account for a considerable portion of the observed discrepancies in the case of H/sub ..cap alpha../, and possibly a small part in the case of H/sub ..beta../ at low electron densities (< or approx. =10/sup 15/ cm/sup -3/).

• Research Organization: Institute for Basic Standards, National Bureau of Standards, Washington, D. C. 20234
• OSTI ID: 5753406
• Journal Information: Phys. Rev., A; (United States), Journal Name: Phys. Rev., A; (United States) Vol. 21:1; ISSN PLRAA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700102* -- Fusion Energy-- Plasma Research-- Diagnostics
BALMER LINES
CRYOGENIC FLUIDS
CURRENTS
ELECTRIC ARCS
ELECTRIC CURRENTS
ELECTRIC DISCHARGES
ELECTRON DENSITY
ELEMENTS
FLUIDS
HYDROGEN
LINE BROADENING
LINE WIDTHS
NONMETALS
PLASMA DIAGNOSTICS
TEMPERATURE DEPENDENCE