Fluorescence of nitrogen and air

Abstract

Electron beams with 12 keV particle energy were used to excite nitrogen and air. Light emission has been studied using two types of optical spectrometers and a calibrated silicon photo diode. The relative intensities of the nitrogen emission bands in air have been measured and compared with data from the literature. The intensity ratio of the v=0 to 0 emission of nitrogen at 337 nm in the second positive system between pure nitrogen and air was determined to 12.9 ± 0.6 for 800 hPa total pressure for the best gas purity achieved in the experiments. Potential underlying gas kinetic processes are discussed. A measurement of the absolute conversion efficiency of electron beam power into light in the 337 nm band of nitrogen is presented. Converting the result into the corresponding value for dry air leads to a value of (6.1 ± 0.5) 337 nm photons emitted per MeV electron beam energy deposited in air at 1000 hPa and room temperature. The corresponding value for 800 hPa is (8.1 ± 0.8)/MeV.