1.Prokhorov General Physics Institute,Russian Academy of Sciences,Moscow,Russia;2.Faculty of Geology,Moscow State University,Moscow,Russia;3.Baikov Institute of Metallurgy and Materials Science,Russian Academy of Sciences,Moscow,Russia
Abstract:
The effect of 21-MeV electron irradiation on the optical absorption characteristics of Czochralski-grown forsterite (Mg2SiO4) single crystals (both undoped and chromium-doped) has been investigated. The irradiation is found to induce additional optical
absorption (AOA) in the crystals in the range of 225–1200 nm due to the formation of color centers based on intrinsic host
point defects and the change in the oxidation state of chromium ions. The AOA spectra have been decomposed into elementary
bands. The influence of the chromium concentration in crystals, the oxygen content in the growth atmosphere, and additional
doping with lithium on the behavior of these bands has been analyzed. A possible structure of the color centers responsible
for the AOA is discussed. It is shown that the electron irradiation somewhat decreases the intensity of the characteristic
absorption bands of tri- and tetravalent chromium ions and gives rise to a new absorption band in Mg2SiO4:Cr and Mg2SiO4:Cr,Li crystals heavily doped with chromium.