The Colour Change and Three-Dimensional Fluorescence Features of Spodumene from Afghanistan Before and After Electron Irradiation

At present, natural spodumene can be modified by irradiation to improve its value, but the information about the spectral characteristics of irradiated spodumene is incomplete. This study aims to analyze the internal defect changes of spodumene through its spectral characteristics before and after electron irradiation, so as to provide certain support for the defect analysis and colour modification process of spodumene. In this study, the light purple-pink and light yellow spodumene samples from Afghanistan before and after electron irradiation were analyzed by UV-Vis spectrum and fluorescence spectrum, and the fluorescence and phosphorescence changes of spodumene before and after irradiation were compared. The results show that after electron irradiation, the colour of the light purple-pink spodumene samples change to emerald green, the pink-orange fluorescence is obviously enhanced, and the pink-orange phosphorescence appears. The light yellow spodumene samples showed an increase in yellow tone and no significant change in fluorescence, while a few yellow samples partially became emerald green, and pink orange fluorescence and phosphorescence were seen in the discolored areas. The UV-visible spectrum results show that the samples show emerald green after irradiation show absorption peak at 630 nm, and the Fe³⁺ absorption peak of the samples that showed partially emerald green after irradiation was weakened in the light yellow samples. Three-dimensional fluorescence spectrum results show that there are λ_em=450 nm, λ_em=610 nm and λ_em=700 nm fluorescence regions in spodumene samples before and after irradiation, and the fluorescence regions are enhanced in different degrees after irradiation. Among the λ_em, it is worth noting that after irradiation, the spodumene that changes into emerald green has an enhanced fluorescence center of λ_ex=350 nm and λ_em=600 nm, which is consistent with the phenomenon of strong pink orange fluorescence. By judging whether there is a 630 nm absorption peak in the UV-Vis spectrum and whether there is an obvious λ_ex=350 nm and λ_em=600 nm fluorescence center (pink-orange fluorescence) in the 3D fluorescence spectrum, it can help judge whether the spodumene has been irradiated.