Optical Emission Produced by Proton and Hydrogen-Atom Impact on Nitrogen

Optical emissions produced in collisions of protons and hydrogen atoms incident on nitrogen molecules were studied in the spectral region from 1200 to 6000 Å. Relative emission cross sections were measured in the energy range from 10 to 130 keV. The prominent features of the nitrogen spectrum below 2000 Å were the Lyman-$\alpha$ line and atomic nitrogen lines. The Lyman-Birge-Hopfield system appeared also, but it was weak. At the longer wavelengths, the $\mathrm{N}_2^{}{}_{}{}^{+}$ first negative and the ${\mathrm{N}}_2$ second positive systems dominated the spectrum. Relative emission cross sections for the production of the first negative bands in collisions of hydrogen atoms with nitrogen molecules were nearly constant as a function of energy, and at an energy of 40 keV the cross section was one-half as large as the cross section for proton collisions. The cross section for the second positive band due to hydrogen-atom impact was about 3 × ${10}^{-18\mathrm{}}$ ${\mathrm{cm}}^2$ at 25 keV, whereas for proton impact the cross section was about 2 × ${10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$ at its maximum value. The cross sections for the atomic nitrogen lines produced in hydrogen-atom impact were approximately 75% of the cross sections for the same lines produced in proton impact. Hydrogen-atom collisions had higher cross sections throughout the energy range for the production of Lyman-$\alpha$ emission.