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A Study of Equilibrium in Argon Arcs
1Institute for Basic Standards, National Bureau of Standards, Washington, D.C. 20234.
Summary
This study examines argon spectral line intensities from wall-stabilized arcs. Departures from equilibrium occur at lower electron densities, but higher densities yield accurate transition probabilities.
Area of Science:
- Atomic Physics
- Plasma Physics
- Spectroscopy
Background:
- Understanding plasma conditions is crucial for various applications.
- Accurate transition probabilities are essential for plasma diagnostics and modeling.
Purpose of the Study:
- To investigate argon spectral line intensities using wall-stabilized arcs.
- To determine conditions under which local thermodynamic equilibrium (LTE) is valid.
- To derive transition probabilities for argon.
Main Methods:
- Utilized wall-stabilized arcs to generate plasma.
- Measured intensities of Ar I (7147 Å) and Ar II (4806 Å) spectral lines.
- Presented data in an Olsen-Richter diagram for analysis.
Main Results:
- Observed departures from local thermodynamic equilibrium (LTE) at electron densities below 5 × 10^16 cm^-3.
- Found that assuming LTE at higher electron densities provided transition probabilities in good agreement with experimental lifetime measurements.
Conclusions:
- Established the electron density threshold for LTE in the studied argon plasma.
- Validated the use of spectral line intensity measurements under LTE conditions for determining transition probabilities.
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