Phosphorescence spectra from alkali feldspars as they are cooled

Abstract

We report here phosphorescence spectra over the range 1.55 to 5.5 eV from three alkali feldspars after irradiation as they are cooled from room temperature to 130 K. The dominant emission was at 1.7 eV. With decreasing temperature, the intensity of this band initially decreased, but then increased below 250 K, consistent with the observation of Visocekas and Zink. We confirm their inference that they were measuring the 1.7 eV emission band characteristic of Fe3+. Other emission bands were observed at 2.2, 2.7 and 4.3 eV; their intensities decreased with decreasing temperature.We were also able to measure the emission spectra of one sample after a 30 minute heating at 120°C; the 1.7 eV band was much reduced and the emission now dominated by the 2.2 eV band, characteristic of Mn2+. The 1.7 eV band now did not show thermal quenching.