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 {}. Relative emission cross sections were measured in the energy range from 10 to 130 keV. The prominent features of the nitrogen spectrum below 2000 {} were the Lyman-α line and atomic nitrogen lines. The Lyman-Birge-Hopfield system appeared also, but it was weak. At the longer wavelengths, the N₂^_⁺ first negative and the N₂ 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 cm² at 25 keV, whereas for proton impact the cross section was about 2 ×{} 10^-19 cm² 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-α emission.