Reflection spectra, the excitation spectra of various emissions (2.4 to 4.5eV) and the creation spectra of F centres were measured in Na6Al6Si6O24(NaBr)2x optical sodalite ceramics (where x was 0.94 or 0.81) by using vacuum ultra-violet radiation of 6 to 35eV. An analysis of the spectra permitted the separation of several groups of electronic excitation. The photons of 6.7 to 8.3eV excited or ionized Br- centres in the β-cages, the 8.5 to 32eV photons generated electronic excitations of the aluminosilicate framework, and the 33eV photons excited Na+ ions up to the 2p53s state. The creation mechanism of F centres, related to the trapping of conduction electrons by pre-irradiation Br vacancies and the localization of holes at Br- centres in β-cages, was revealed at 80K. The efficiency of F-centre creation tripled within the multiplication region of electronic excitations of the aluminosilicate framework (20 to 30eV), in samples with x = 0.94. By using thermo-activation spectroscopy, the creation of thermally stable F centres (up to 480K) was detected in sodalites which were irradiated with X-rays or 27eV photons. However, such F centres could not be created by 7.6 to 11eV photons; that is, when there was no multiplication of excitations and an exciting photon formed only 1 electronic excitation.

Creation of F Centres and Multiplication of Electronic Excitations in Na6Al6Si6O24(NaBr)2x Optical Ceramics under VUV Irradiation. C.Lushchik, V.Demidenko, M.Kirm, I.Kudryavtseva, A.Lushchik, I.Martinson, V.Nagirnyi, E.Vasilchenko: Journal of Physics - Condensed Matter, 2001, 13[27], 6133-49