Luminescence of molecular O2- ions in neutron-irradiated Be2GeO4Be2GeO4

The low-temperature time-resolved photoluminescent spectroscopy with synchrotron excitation was used to analyse samples of polycrystalline Be2GeO4Be2GeO4 after exposure to fast neutrons (E∼1MeV; Φ=4.5×1017cm-2). Luminescence spectra of the test samples contained the band at 1.7 eV arising from the radiative relaxation of neutron-induced molecular O2- ions. Luminescence of these defects was efficiently excited by photons with an energy of 4.7 and 5.2 eV. Contours of the corresponding bands in the photoluminescence and excitation spectra of O2- centres had a characteristic fine structure, which reflected the presence of intracentre interactions. Average vibration frequencies of O2- ions in the Be2GeO4Be2GeO4 lattice were determined. Potential energy curves were calculated using the Morse potential for the ground and excited states of molecular O2--ions in Be2GeO4Be2GeO4.