A measurement of the air fluorescence yield

We measured the air fluorescence yield as a function of pressure with electrons between 1.4 and 1000 MeV by means of a Sr-90 beta source and an electron beam. Results indicate that the fluorescence yield is proportional to electron energy loss from 1.4 to 1000 MeV. The dE/dx relativistic rise in air is detected. We describe the pressure temperature dependency of air fluorescence by a formula derived from simple kinetic theory. With the aid of the 1966 US Mid-latitude Standard Atmospheric Model, we calculate the altitude dependence of fluorescence yield of an 80 MeV electron which demonstrates how this measurement could improve the longitudinal particle density profile determination of extensive air showers (EAS) observed by detectors such as the High Resolution Fly's Eye and the Telescope Array.