Angular Dependence of Ionoluminescence for Silica Case

Abstract

The paper deals with angular dependence of ionoluminescence from transparent glossy silica samples. We measured silica ionoluminescence spectra at wavelength range of 400–700 nm for different projectiles (H1+, H2+, He+ 210 and 420 keV) and registered two most common intensive emission peaks (blue with a maximum at 456 nm and red one at 645 nm). To study luminescent angular dependence, the behavior of the blue peak maximum as a function of observation angle in the range of 0–70° was examined, namely, the indicatrix at the wavelength of 456 nm was found. The intensity corresponding to ionoluminescent indicatrices were found to be higher with respect to values from Lambertian angular distribution reaching approximately 20 % at large observation angles. We also calculated angular distribution of light above the sample surface taking into account refraction and reflection at the solid-ambient interface. The results obtained were in a good agreement with silica ionoluminescence experimental data for the average indicatrix curve. The latter indicates that the model assumption (luminescent light generated by fast ions within silica is unpolarized and isotropic) is correct. It was demonstrated that geometry of the experiment is very important, i.e., considering the light collected by the measuring system in a certain solid angle, one has to take into account that mutual arrangement of the sample and detector can distort angular distribution. The refraction at the border between a sample and vacuum (or air) strongly influences the luminescent light angular distribution.