Optical Radiation from Nitrogen and Air at High Pressure Excited by Energetic Electrons

Abstract

The spectral characteristics and fluorescent efficiencies for electron excitation of nitrogen and air at 600 Torr have been determined. Results are presented for the efficiency of conversion of electron energy to optical radiation in approximately one hundred resolved spectral components of air and nitrogen between 3200 and 10 800 Å when bombarded by 50-keV electrons. The total fluorescent efficiency under these conditions is (0.14±0.02)% for nitrogen and (6.7±1.0)×10—3% for air. In nitrogen the first positive (B 3Πg→A 3Σu+), second positive (C 3Πu→B 3Πg), Gaydon green, Herman infrared, and Goldstein—Kaplan (C′ 3Πu→B 3Πg) band systems of N2 and the first negative (B 2Σu+→X 2Σg+) band system of N2+ were observed. The (0–2) and (0–3) transitions of the Herman infrared system and [N I]32(2D—2P) forbidden doublet at 1.04 μ, previously unreported in the laboratory, were observed. In air the first positive and second positive band systems of N2 and the first negative band system of N2+ were observed as well as atomic spectra of nitrogen, oxygen, and argon.

Photon yields from nitrogen gas and dry air excited by electrons

“…(10) for a limited range of pressures. [14] are about a factor of 2.8 larger than the present results except at 391 nm and 400 nm.…”

“…In order to apply the present measurements to air shower fluorescence experiments, the fluorescence yields per meter per electron must be known as a function of air The total photon yield between 300 nm and 406 nm given by Bunner is about 14 % smaller than the present corrected results. His value was obtained as weighted averages of three measurements by Davidson and O'Neil (50 keV electrons) [14], Hartman (electrons, cited from [5]) and Bunner (alpha particles) [5], and the accuracy of each of the three experiments was not better than ±30 % [5]. Therefore the disagreement may be within their measurement errors.…”

“…(11), after replacing R N 2 by R air =287.1 m 2 s −2 K −1 and by using p i given by Eq. (14). The values of Φ i (p) in air at 800 hPa are listed in Table 6 together with results of other experiments.…”

Optical characteristics of red sprites produced by runaway air breakdown

“…To calculate the intensity of the optical emissions, we use the air fluorescence efficiencies measured by Davidson and O'Neil [1964], and Mitchell [1970], and quenching rates measured by Mitchell [1970]. We note, however, that the efficiencies were measured in the absence of an externally applied electric field and therefore only account for part of the optical emissions associated with a runaway discharge.…”

Techniques of the FLASH thin target experiment

“…Emission is dominated by transitions within the ni- * Corresponding author. E-mail address: petra@cosmic.utah.edu trogen molecular band systems, near 315, 337, 355, 380 and 391 nm, with others of lesser intensity [1,2].…”