Calculated and measured line intensity ratios of singly and doubly ionized nitrogen atoms in hydrogen plasma
The oscillator strengths of several NII and NIII lines in the optical wavelength region are calculated by means of the Coulomb approximation. Atomic processes in a plasma are discussed, as well as two models (LTE and semi-coronal) which can be used to determine the line intensity ratios of subsequent ionization stages of the same element. Two derivations of line intensity ratio formulae are given, valid under LTE and semi-coronal conditions. Parameters necessary for the evaluation of collisional-radiative coefficients in the semi-coronal model are discussed, and an attempt is made to show that the theoretical values in the literature at present, are inadequate under the laboratory conditions of interest. The lines for which f-values have been calculated are generated in a theta pinch plasma, and an attempt is made to decide which of the two models accounts more accurately for the observed intensity ratios.
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