RADIATION STUDIES OF ARC HEATED NITROGEN, OXYGEN, AND ARGON PLASMAS

This report presents continuum radiation and line radiation measurements for nitrogen, oxygen, and argon covering wavelength ranges from the vacuum ultraviolet to the infrared for a selection of pressures and temperatures. A mechanically constricted dc arc was used as the radiation source. Nitrogen continuum data at 1 and 2 atmospheres is reported for wavelengths from 700 to 37,000 A and temperatures from 9,000 to 13,500 K. The spectral data have been treated analytically to separate the radiation from electron-neutral atom and electron-positive ion collisions, and comparison is made with the theory of Burgess and Seaton for the positive ion recombination radiation. Values of the ratio, R, by which this theory differs from our experimental results are given as a function of wavelength. A subtraction of the positive ion radiation from the total continuum yields the contribution from the neutral atom, from which was extracted the approximate absorption edges of the nitrogen negative ion and an estimate of the photo-detachment cross section. Earlier data reported for the argon continuum at atmospheric pressure has been improved by a reinterpretation of the temperature measurement. New argon continuum intensities at 5 atmospheres pressure and 12,300 K are reported. (Author)