Optical absorption spectra of neutron-irradiated Li2O

Abstract

Radiation damage in neutron‐irradiated Li2O is investigated by optical absorption measurements for single crystals as well as sintered pellets. The results obtained in this study are as follows: (1) The optical absorption bands are observed at 310, 375, 570, 720, 800, and 1100 nm; the 310 nm band is assigned to the F+‐center band. (2) A series of sharp bands is observed at the longer wavelength side of the 800 nm band for heavily irradiated Li2O; they seemed to be zero‐phonon line and vibrational sidebands. (3) Radiation damage in Li2O is mainly induced by energetic tritons and helium ions produced by the 6Li(n, α)3H reactions and fast neutrons, and the efficiency of the defect production in Li2O by the collision of fast neutron is determined to be about five times larger than that of the 6Li(n, α)3H reaction.

The F+‐Centre in Alkali Oxides of Antifluorite Structure. a Model Potential Numerical Calculation

“…AS a primary step, me employ the PI model to calculate hydrogen like energy states, namely IS and 2p levels. The results listed in Table 1 are for the F+-centre in four oxides, the transition energy of 4.76 eV in the Li,O case compares favourably with the absorption band peak of 4.0 eV reported by Uchida et al [8]. Experimental data in other oxides are, unfortunately, not available a t the present time.…”

“…Following Gourary and Adrion [5], the true wave function Up can be related approximately to the pseudo-wave function @* through an appropriate amplification factor M f by l%.+(j)l2 = 311 l@p(j)tz, (8) where Nj is calculated from free ion orbitals [12,171 under the assumption that @ is a slowly varying function over core orbitals and is, thus, a property of a given ion species.…”

Low-temperature irradiation effects in lithium orthosilicates

“…in the region of the efficient excitation of 5-eV emission [20]. In Li 2 O single crystals at 9 K, two emission bands at 3.7 eV (hm exc = 6.8 eV) and 4.75 eV (hm exc = 7.7 eV) [11], as well as the 4-eV absorption band related to the so-called F + centers (an electron in the field of an anion vacancy) [9,10] have been revealed. One might expect the analogous emissions of STEs, F and F + centers in Li 4 SiO 4 ceramics as well.…”

“…These peaks were ascribed to the annealing of the charged defects that served as the traps for highly mobile tritium. An example of such traps is F + centers, which have been thoroughly studied in Li 2 O crystals [9,10]. The spectrum of radiation-induced optical absorption consists of F + -band peaked at $4 eV and a broad band at 1.7-2.3 eV.…”

“…A Li 4 SiO 4 complex compound consists of SiO 4 tetrahedrons and small-radius Li atoms bonded to the oxygen atoms. The results of long-standing investigations of the physical processes in a-SiO 2 crystals and other silicates [6][7][8], as well as in Li 2 O single crystals and ceramics [9][10][11][12], will be useful for the study of lithium orthosilicates. The main applications of Li 4 SiO 4 ceramics are expected at temperatures close to the melting point (1230°C) of the material.…”