Bremsstrahlung and Recombination Radiation of Neutral and Ionized Nitrogen

Abstract

Continuum radiation measurements are presented for nitrogen over a spectral range from 975 to 37 000 \AA{} for temperatures ranging from 9000 to 13 500\ifmmode^\circ\else\textdegree\fi{}K and 1- and 2- atm pressure. The measurements were made using a plasma produced in a dc mechanically constricted arc generator. The data is separated by a temperature-dependence curve fit into the contributions from positive-ion and neutral-atom radiation. The ${\mathrm{N}}^{+}$ radiation is compared to an analytical calculation based on the Burgess and Seaton quantum-defect method for the free bound and on the Gaunt factors of Karzas and Latter for the free-free processes. The remaining radiation in the visible and infrared is ascribed to the neutral atom. This data is analyzed to derive the ${\mathrm{N}}^{\ensuremath{-}}$ species responsible for the recombination radiation and to extract its ionization energy from the position of observed absorption edges. A value for the (${\mathrm{N}}^{\ensuremath{-}}^{1}D$) negative-ion cross section is obtained. Extraction of the neutral atom ${Z}^{2}g$ factor for the Bremsstrahlung process was made from the continuum data in the infrared. Comparison is also made to other experimental data.