Determination of the chemical states of iron in plagioclase by external beam ionoluminescence

A facility for the detection of ionoluminescence (IL) induced by a 2.4 MeV external proton beam was introduced. The chemical states of iron in a plagioclase sample were analyzed by the external beam IL method. The various intervals of luminescence wavelength were selected by light interference filters and collected by a photo-multiplier tube (PMT). After the data handling of various corrections for different factors and linear polynomial fitting of the experimental data, both ferrous and ferric iron peaks (Fe2+, Fe3+) from the plagioclase sample were apparently observed in the IL emission spectrum. The two peaks near 553 nm (2.241 eV) and 682 nm (1.817 eV) corresponding to Fe2+ and Fe3+ were shown, respectively.