Comparison of photoconductivity and optical absorption spectra of trapped electrons in γ-irradiated 2,2,4-trimethylpentane/2,2-dimethylbutane/2-methyltetrahydrofuran mixture glasses at 77 K

Abstract

TOYOAKI KIMURA, KAZUNOBU HIRAO, NAOTO OKABE, and KENJI FUEKI. Can. J. Chem. 62, 64 (1984). Optical absorption and photoconductivity spectra of trapped electrons in y-irradiated 2,2,4-trimethylpentane (TMP)/2,2-dimethylbutane (DMB)/2-methyltetrahydrofuran (MTHF) mixture glasses at 77 K have been measured. It is found that the magnitude of the photocurrent increases with decreasing MTHF concentration, which is ascribed to the increase in electron mobility with decreasing MTHF concentration in TMP/DMB/MTHF systems. It is also found that the photoconductivity spectra shift to the lower energy side with decreasing MTHF concentration. Although the photoconductivity spectrum in the neat MTHF system is separated from the corresponding optical absorption spectrum, the spectrum becomes closer to the latter with decreasing MTHF concentration in TMP/DMB/MTHF systems. This result indicates that the extent of bound-free transitions increases relative to bound-bound transitions with decreasing MTHF concentration for the photon absorption process of trapped electrons in TMP/DMB/MTHF systems.TOYOAKI KIMURA, KAZUNOBU HIRAO, NAOTO OKABE et KENJI FUEKI. Can. J. Chem. 62, 64 (1984). On a mesurC a 77 K les spectres d'absorption optique et de photoconductivitC des tlectrons piCgCs dans un melange vitreux de trimCthyl-2,2,4 pentane (TMP)/dimtthyl-2,2 butane (DMB)/mCthyl-2 tktrahydrofuranne (MTHF) irradiC aux rayons y. On a trouvC que l'intensitt du photocourant augmente lorsque la concentration du MTHF diminue, ce qui l'on attribue a une augmentation de la mobilitk de l'tlectron lorsque diminue la concentration du MTHF dans le systbme TMP/DMB/MTHF. On a Cgalement trouvt que les spectres de photoconductivitt glissent du cat6 de faible Cnergie lorsque la concentration de MTHF diminue. Bien que le spectre de photoconductivitC du systeme MTHF pur soit separe du spectre correspondant d'absorption optique, ces deux spectres se rapprochent beaucoup lorsque la concentration de MTHF du systkme TMP/DMB/MTHF diminue. Ce rCsultat indique que le taux de transitions liaison-libre augmente par rapport aux transitions liaison-liaison lorsque la concentration de MTHF diminue dans le processus d'absorption du photon pour les electrons piCgCs dans le systbme TMP/DMB/MTHF.[Traduit par le journal] I

A photoconductivity study in γ-irradiated polyethylene at 77 K

“…The scheme of the experiment was the same as that in ref. 25. A dc voltage of 500 V was applied for a sample of 1 mm thickness (5 kV/cm).…”