Study of Emission and Absorption Properties of Natural and Artificial Glasses Exposed by Gamma Irradiation

Samples of natural glass (translucent obsidian) and artificial glass obtained from natural perlite raw material and similar in composition to obsidian were irradiated at room temperature by γ‑photons with an average energy of 1.25 MeV in different doses up to 1300 kGy from a ⁶⁰Co radiation source. It is known that γ-radiation affects the optical properties of glass depending on the composition as well as on the presence of defects in the glass framework. The analysis was carried out using the methods of absorption, luminescence, Raman, and EPR spectroscopy depending on the γ-irradiation doses. A comparison of the transmission, photoluminescence, Raman, and EPR spectra for obsidian and perlite glass was carried out. The difference transmission spectra between non-irradiated and irradiated samples made it possible to isolate the absorption bands for which Fe³⁺ ions in different coordination are responsible. Upon excitation with a laser with a wavelength of 473 nm, visible to the naked eye green–red photoluminescence was observed in natural and synthetic glasses before and after irradiation. Raman spectra upon excitation with a wavelength of 785 nm in both types of studied glasses before and after irradiation showed vibrational frequencies characteristic of glass matrices and a band associated with water in the silicate network of glass. In addition, during the registration of the Raman spectra, an intense asymmetric photoluminescence band was observed in the 850–950 nm region. EPR measurements showed three signals characteristic for Fe³⁺ ions with g-factors of ~6.0, ~4.2 and ~2.0 in natural and synthetic glasses. In the region of the specified doses of γ-irradiation, obsidian and perlite glass turned out to be resistant to the formation of NBOHC paramagnetic defects.