Pergamon zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA J. Quant. Spectrosc. Radiat. Transfer Vol. 56, No. 3, 377-398, 1996 pp. Copyright 0 1996 Elsevia Science Ltd PII: S0022-4073(%)00060-X Printed in Great Britain. All rights reserved 0022-4073/96 $15.00 + 0.00 LINE-BY-LINE METHOD OF CALCULATING EMISSION COEFFICIENTS FOR THERMAL PLASMAS CONSISTING OF MONATOMIC SPECIES J. MENART, J. HEBERLEIN,? and E. PFENDER Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, MN 55418. U.S.A. (Received 15 November 1995) Abstract-A theoretically rigorous method for obtaining radiation property data of thermal plasmas composed of monatomic, nonhydrogenic species is presented. An exact line-by-line technique is utilized in order to avoid assumptions that are commonly made in handling line radiation. Doppler, natural, Van der Waals, resonance, and quadratic Stark broadening mechanisms are included in determining the line half-widths. In addition to line radiation, free-bound continuum and free-free continuum for both ions and neutral particles are considered. The fundamental radiation property determined by the program is the spectral emission coefficient. From this property the spectral absorption coefficient can easily be determined. Properties that are more suitable for engineering analysis, such as the wavelength integrated emission coefficient and the net emission coefficient, are also calculated. Comparisons to experimentally determined wavelength integrated emission coefficients for argon plasmas and analytically determined net emission coefficients for argon/copper plasmas are presented. Copyright 0 1996 Elsevier Science Ltd 1. INTRODUCTION To accurately model a plasma’s thermal characteristics good radiation property data is required. There is some radiation property data in the literature, but not a large amount. To help fill this void a program has been written which calculates the spectral emission coefficient. Utilizing the spectral emission coefficient, the wavelength integrated emission coefficient and net emission coefficient as introduced by Lowke’ are determined. If the spectral absorption coefficient is required it can easily be obtained from the spectral emission coefficient by using Kirchhoff’s law. In this paper the fundamental equations used to calculate the spectral emission coefficient for thermal plasmas consisting of monatomic, non-hydrogenic species are presented. It is the intent to present as many of the equations as possible, citing references for those equations that need to be eliminated because of space considerations. An expanded presentation of the method and results can be found in Ref. 2. Bound-bound, free-bound, and free-free transitions in an atom or ion are the radiative emission mechanisms included. Neglected in this analysis are the cyclotron/synchrotron, vibrational, rotational, and chemical emission mechanisms that can be present in plasmas. The vibrational, rotational, and chemical emission mechanisms all have to do with molecular species. The cyclotron/synchrotron radiation is due to electrons spiraling in strong magnetic fields. This mechanism does not need to be included except in cases where extremely strong magnetic fields are present. The calculation approach for obtaining emission coefficients as a function of wavelength is similar to that used by Park.3 The main similarity that exists between this work and that of Park is both utilize a line-by-line technique. Park was not directly interested in emission coefficients in his paper, but in radiative heat transfer through a shock induced plasma layer. No emission coefficients were presented by Park, but they were part of his intermediate calculations. Practically, tTo whom all correspondence should be addressed. 317