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RESEARCH PRODUCT
Bleaching and thermal recovery of PL emissions in natural silica
Marco CannasFranco Mario GelardiSimonpietro AgnelloRoberto BoscainoMaurizio Leonesubject
Nuclear and High Energy PhysicsPhotoluminescenceThermal recoveryChemistryAnnealing (metallurgy)Low doseAnalytical chemistryOptically activelaw.inventionParamagnetismlawElectron paramagnetic resonanceInstrumentationHyperfine structuredescription
Abstract We have investigated the bleaching of two photoluminescence (PL) emissions at 3.1 and 4.2 eV and the related growth of an electron spin resonance (ESR) signal, consisting in a hyperfine doublet split by 11.8 mT, in natural silica γ-irradiated by low doses, up to 1 Mrad. These observations definitely support the existence of a conversion mechanism, from optically active defects to paramagnetic ones. To further investigate this conversion process and the stability of the γ-induced paramagnetic centers, we performed PL and ESR measurements in samples that, after a γ exposure at 1 Mrad dose, were thermally treated at various temperatures ranging from 330 to 430 K. We found that the intensities of PL and ESR signals recover their pre-irradiation values, that is the PL bands intensities are completely restored and the 11.8 mT doublet disappears at all. These features give evidence of a thermally activated back-conversion mechanism, from the paramagnetic center to the optically active one, able to restore completely the structure of the latter defect before γ-irradiation.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2000-05-01 | Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms |