Scintillation response of nonactivated and activated NaI to random and channeled ions: Influence of the luminescence mechanism

Previous experiments have shown that the scintillation response to random positive-ion bombardment of alkali iodides, both nonactivated and activated, have similar characteristics even though the luminescence mechanisms are very different. This paper reports experiments on nonactivated NaI and NaI(Tl). The relative pulse height as a function of energy for randomly incident protons (3-14 MeV) and ¹⁶O ions (5-50 MeV) for both crystals has been recorded. Also, pulse-height spectra due to energetic ¹⁶O ions (10-50 MeV) channeled along the {100} plane and $〈100〉$ axis of nonactivated NaI at 100^∘{}K are presented and compared with those obtained previously for NaI(Tl). The following observations are made: (i) The ratio of the relative number of photons per unit energy for ¹⁶O ions to that for protons is very nearly the same for both crystals. (ii) The ratio of light outputs for totally channeled particles to random particles is nearly the same for both crystals. (iii) The detailed characteristics of pulse-height spectra from channeled ions are very similar for the two crystals. These results indicate that the scintillation response is quite insensitive to the particular luminescence mechanism.