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Optical effects by high energy electrons in additively colored KCl and KBr crystals

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Radiation effects of high energy electrons on pure and additively colored (AC) KCl and KBr crystals have been studied by optical absorption in the 200-800 nm range at RT. Besides the main F-center related absorption band at 553 nm, the F+ 2 (670 nm) and F2 (740 nm) bands (R1 and R2 centers in old notation) ascribed to F centers aggregates in additively colored KCl are clearly observed. After electron irradiation with energy of 1.0 MeV and doses of 100 kGy or 3.5 MeV and 180 kGy, the F+ 2 and F2 bands are strongly diminished, the intensity of the F bands is increased and its peak lightly shifted to low energy at 558 nm. In KBr, the related absorption band maximum for the pure and AC samples after irradiation shows the same peak position as the F-center absorption. For AC KBr the intensity of this peak versus accumulative doses shows a maximum around 300 kGy but in pure KBr the peak continuously increases. In contrast, KCl does not show such dependence on accumulative doses. For both samples, the electron irradiation induce at least two bands in the 210-300 nm (UV bands) range that has been related with hole centers (V bands). The results have been analyzed in terms of surface close F centers and alkali and halogen ions desorption processes.


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