M.R.Baril and D.J.Huntley.

Optical excitation spectra of trapped electrons in irradiated feldspars.

Journal of Physics: Condensed Matter 15, 8011-8027, 2003.

Abstract

The dependence of optically stimulated luminescence spectra on the energy of excitation photons has been investigated for a wide range of feldspars. In the vicinity of the 1.44 eV resonance, the spectra are in many cases best described by a Voigt profile with a minor Lorentzian component centred at 1.44 eV. Most samples display a second excitation resonance near 1.57 eV, and more rarely a third peak at 1.3 eV. The shape of the excitation spectrum is the same for both the violet (3.1 eV) and yellow-green (2.2 eV) emission bands and, for one sample, the UV band (3.3-3.7 eV). The shape of the excitation spectrum is unaffected by the polarization direction of the excitation beam. The principal resonance at 1.44 eV broadens little, if at all, with increasing temperature over the range 290-490 K. The initial luminescence decay rate as a function of the initial luminescence intensity per unit energy was determined over a wide range of excitation energies (1.24-2.58 eV) for four feldspars. In every case, the initial slope was observed to increase linearly with the square of the initial intensity over the range 1.24-2.4 eV. All this provides strong evidence that excitation is from a single trap located at least 2.5 eV below the conduction band.