Luminescence excitation characteristics of Ca-, Na- and K-aluminosilicates (feldspars), in the stimulation range 20 500 eV: optical detection of XAS

We demonstrate that the visible/UV luminescence from common feldspar crystals (NaAlSi₃O₈, KAlSi₃O₈ and CaAl₂Si₂O₈) can be used to detect detailed L-edge and associated near-edge absorption structure of the main constituent atoms (Ca, K, Na, Al, Si), when exciting in the energy range 20-500 eV. Comparisons of the spectral features are drawn with similar measurements made on the associated materials SiO₂, Al₂O₃ and CaCO₃. The potential for using optically detected x-ray absorption spectroscopy as a method for identifying the luminescent components of mixed mineral samples is considered.