Ionizing radiation acts on 3:2 KNO3-Ca(NO3)2 glasses to produce a simple hole center, the NO3 radical, and an excess electron center, which is probably the NO32- radical. At 297 K, 10-6 s after a 4-ns pulse of radiation a yield of 3.2 ± 0.2 ion pairs is found per 100 eV of absorbed energy. The ion pairs recombine, as observed by following the red absorption of NO3 (λmax 615 nm), from 10-6 to 102 s. Diffusion of the reacting species is involved above the glass transition temperature (Tg = 341 K), while electron tunneling seems to be the main mechanism below Tg. The reaction is weakly temperature dependent (EA ≃ 3 kcal) from 77 to 260 K, but EA jumps to ≈ 18 kcal above 260 K. These results are discussed in terms of modern electron-transfer theories, which predict such a transition from weak to strong activation. Acetate glasses showed no detectable radiation coloration in the visible, and only a small, decaying absorption in the near UV.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry