Laboratory studies of UV emissions from proton impact on N₂: The Lyman-Birge-Hopfield band system for aurora analysis

Abstract

[1] We have measured the emission cross sections of the Lyman-Birge-Hopfield (LBH) a 1Πg − X1Σg+ band system and several atomic nitrogen (N I) multiplets (1200, 1243, 1493 Å) by H+ (proton) impact on N2 over an impact energy range of 1–7 keV. The peak proton-impact-induced emission cross section of the LBH band system (1260–2500 Å) was measured to be 5.05 ± 1.52 × 10−17 cm2 at 7 keV. To the best of our knowledge, the present LBH emission cross sections are reported for the first time in the far ultraviolet (FUV) wavelength range of 1100–1600 Å. The proton energy range in this study, when coupled with previously published 10–100 keV proton excited emissions of N I multiplets, provides a wide energy range of emission cross sections for proton energy loss transport codes. This energy range includes the peak cross section and the energy range for Born scaling. The reported measurements lead to an important component of monoenergetic yields for proton FUV auroral emission. Such yields, based on emission cross sections and transport modeling, allowed for convenient comparison of emission efficiencies between proton and electron aurora. In addition, we have measured the H Ly α, LBH, and N I multiplet emission cross sections for H2+ and H3+ ion impact on N2 at 5 keV and found that the magnitude of H Ly α emission cross section, σem(Ly α), follows in the order of impact ion mass H3+ > H2+ > H+.