Effects of swift heavy ion irradiation parameters on optical properties of muscovite mica

Muscovite mica sheets with a thickness of 25 μm were irradiated by various kinds of swift heavy ions (Sn, Xe and Bi) in HIRFL (Heavy Ion Research Facility in Lanzhou). The fluences ranged from 1 × 1010 to 8 × 1011 ions/cm2 were applied. The electronic energy loss (dE/dx)e in mica was changed from 14.7 to 31.2 keV/nm. The band gaps and Urbach energy of pristine and irradiated mica were analyzed by ultraviolet–visible spectroscopy (UV–Vis). A red shift of the absorption edge was found in the absorption spectra of muscovite mica irradiated by ions with increasing (dE/dx)e. The results show that the chemical bonds between Tetrahedral–Octahedral–Tetrahedral (TOT) layers of mica were destroyed by ion irradiation. With increasing (dE/dx)e and fluences, the band gaps became narrow and the Urbach energy increased. It suggests that the amount of defects and the proportion of amorphous structure were increased in mica irradiated with increasing (dE/dx)e and fluences.