The Fluorescent Response of NaI(Tl) and CsI(Tl) to X Rays and   Rays

Detailed and careful measurements have been made of the light output L γ from NaI(Tl) and CsI(Tl) for energies E γ from 6 kev to 200 kev, employing filtered characteristic x rays and γ rays from radio-active sources; an accuracy of 0.3% for L γ / E γ is claimed. The measurements have been extended, in less detail, to 2.6 MeV. The scintillation efficiency for single electrons, in the energy range 1 keV to 100 keV, calculated from the observed values of L γ / E γ , has been found to be a maximum at 15 keV and at lower energies shows a marked falling off. The results for single electrons are in good agreement with the diffusion theory of Meyer and Murray.