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Title: The spectroscopic study of an electrodeless discharge in argon at atmospheric pressure
Author: Johnston, Philip Douglas
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1969
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The determination of temperature in discharge sources such as plasma jets, arcs, and shock tubes, can be made by a simple method involving the measurement of the relative intensities of spectral lines emitted by the discharge, provided their transition probabilities are known and the conditions of local thermodynamic equilibrium, (L.T.E), pertain to the discharge. The more transition probabilities available and the greater the spread of the appropriate upper energy levels, the better the accuracy of the temperature determination. With a view to measuring transition probabilities in neutral argon, a new type of discharge, the radio-frequency discharge at atmospheric pressure was investigated. A previous temperature measurement of a similar discharge operating under similar conditions was shown to be incorrect by a factor of 2 owing to an erroneous interpretation of the results of a method inapplicable to this type of discharge. The radio-frequency discharge was shown to operate within the conditions of local thermodynamic equilibrium and was proved to be eminently suitable for the measurement of transition probabilities, A reversal technique for temperature determination was adapted to this discharge and, once the temperature had been obtained to a high degree of accuracy, the intensities of 116 neutral argon lines were measured and their transition probabilities determined. Many of these lines had never been measured before, consequently, to afford some comparison, the transition probabilities were calculated in LS, J1j and intermediate coupling. These calculations considerably extended any previous calculations and, where there was duplication with the only previous calculation, eight significant discrepancies were found.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available