Polycrystalline samples preliminarily irradiated by fast neutrons (E ∼ 1MeV, Φ 4.5 x 1017/cm2) were studied by photoluminescence spectroscopy using synchrotron radiation pulses for excitation. The neutron-induced luminescence band observed at 1.7eV in the spectra of the irradiated samples was attributed to the radiative relaxation of a molecular ion O2- . The luminescence of these defects in the Be2GeO4 structure was effectively excited by 4.7- and 5.2eV photons. At low temperatures (10K), the profiles of the photoluminescence and excitation bands have a fine structure characteristic of electron-vibration interactions. The vibration frequencies for the ground state (v1 = 161/cm) and 2 excited states (v2 = 672/cm and v3 = 887−1451/cm) were measured. Potential curves of the energy states of the O2- center were constructed in terms of the Morse model using the experimental data. The optical spectrum fine structure was shown to be predominantly due to intrinsic vibrations of the molecular defect.

Neutron-Induced Molecular Defect O2− in Beryllium Orthogermanate. A.F.Zatsepin, L.A.Blaginina, A.I.Kukharenko, V.A.Pustovarov, S.O.Cholakh: Physics of the Solid State, 2007, 49[5], 839-44