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  • 1 Technical University Institute of Radiation Chemistry Lódz (Poland)
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Abstract  

In the irradiated polar systems, the blue shifts of the absorption spectra of trapped electrons (e t ) have as yet been observed by pulse radiolysis in the milisecond time range. This fact has been ascribed to the reorientation of the matrix polar molecules under the influence of the coulombic electron field. In order to check whether the spectral changes of e t are limited to very short times only, the spectra of e t in frozen 8M NaOH, 95% ethylene glycol (EG), 95% methanol, 95% ethanol, 95% n-propanol, 95% isopropanol, 95% butanol (+5% H2O) were examined at the liquid nitrogen temperature by applying the stationary γ-radiolysis. Except for 8M NaOH and 95% EG, in the remaining matrices the shifts of e t spectra towards the short wavelengths were observed within 24 hrs after irradiation. The less polar the matrix, the larger was the spectral shift. The observed effect seems to indicate that the reorientation process takes place in times much longer than these measured by pulse radiolysis. After the addition of scavengers the lowering of the initial absorption occured in all investigated systems. This was ascribed to the reaction of “dry” electrons with the scavengers. Moreover, the results obtained by the pulse radiolysis of ethanol indicate that the presence of scavengers accelerates the decay of the infrared part of the trapped electron spectrum. The “infrared electrons” (located in shallow traps) neither react with the scavenger nor deepen their traps by reorientation. Most probably in the presence of scavengers these electrons recombine with positive ions via tunneling.