UV optical absorption spectra analysis of spodumene crystals from Brazil

The spectral decomposition analysis was applied to the optical absorption spectra of spodumene crystals from the Brazilian eastern pegmatitic province. The analyzed samples were natural, treated at 400 °C for 24 h and those irradiated with γ rays of 60Co with doses up to 5 MGy. The attributions of the lines were made taking in account highly accurate quantum mechanical calculations. The heated sample had only three lines, which were not affected by irradiation. One of them at 7.58 eV was attributed to an oxygen vacancy defect and the other two at 5.07 and 4.64 eV to a peroxy-type defect. The analysis of the growth of the lines with the irradiation showed that they belong to two groups of defects. The first group of lines at 4.2, 5.3 and 5.9 eV was attributed to a silanone-type defect. The other group of lines at 1.36, 2.0, 2.6, 3.6 and 5.0 eV was attributed to a type of Mn3+ defect. The natural and irradiated samples also showed a line at 2.3 eV, which was attributed to another type of diamagnetic Mn3+ defect.