Intense radioluminescence of NO/N₂-mixture in solar blind spectral region

Luminescence in air induced by alpha particle emitters can be used to optically detect radioactive contamination from distances that surpass the range of the alpha radiation itself. Alpha particles excite nitrogen molecules in air and the relaxation creates a faint light emission. When the composition of the gases surrounding the alpha particle emitter is altered then the luminescence spectrum changes. In this work, we report the creation of an intense light emission in the wavelength regime below 300 nm originating from alpha particle excited nitric oxide (NO). The light yield has been investigated as a function of the NO concentration in an N₂ atmosphere. Unlike the emission from molecular nitrogen, NO emits at wavelengths shorter than 300 nm, where solar background and artificial lighting are negligible, thus enabling optical detection of alpha radiation even under bright lighting conditions. We show that the radioactively induced NO emission reaches its maximum intensity at a concentration of 50 ppm of NO diluted in N₂. At this concentration, the strongest emission line of NO is about 25 times more intense than the most intense line of N₂ radioluminescence. Lastly, we discuss potential applications and limitations of the technique.