Electron Traps in Irradiated Water–Ethylene Glycol Glass at 4 and 77°K

Abstract

In order to study the mechanism of electron trapping in irradiated glasses of water–ethylene glycol mixture, they were subjected to γ rays and examined by optical absorption and electron spin resonance measurements at 4 and 77°K. Most trapped electrons formed at 4°K give an optical absorption band in infrared region around 1800 nm and a single-line electron spin resonance spectrum with the width of 3 G, while the trapped electrons formed at 77°K give an absorption band in visible region (λmax = 585 nm) and an electron spin resonance spectrum with the width of 15 G. By warming the glass to 77°K after the irradiation at 4°K, the trapped electrons transformed to those observed for the irradiation at 77°K. Results indicate that the nature of trapped electrons formed at 4°K is very similar to that of trapped electrons in irradiated nonpolar alkane glasses. Even in the polar glass of water–ethylene glycol, the orientation of molecular dipoles is not needed for the formation of electron traps at 4°K, where the molecular movements are highly restricted. By raising the temperature to 77°K, the molecular dipoles in the vicinity of trapped electrons orient favorably to deepen the traps. The yield of trapped electrons, for 100 eV energy absorbed, at 4°K is estimated to be larger than 0.6. However, it is possibly less than 2.0, the yield for the irradiation at 77°K.

Temperature dependence of the recombination fluorescence of photoionized indole and N,N,N',N'-tetramethyl-p-phenylenediamine in organic glasses. Consequences of electron tunneling and diffusion

“…This process is clearly temperature dependent as shown by experiments in liquids4,18,19 while in many matrices at 4 K the dipole orientation around the electron is complete at very long times. 3,20 Recent careful studies of the electron trap deepening indicated by its spectral shift have shown that even in polar alcohol matrices such as ethanol this spectral shift at 77 K is observable up to about 1 s.17,21 Thus we expect that this trap deepening effect will in fact be occurring before and during the time window that we see in our recombination fluorescence experiment.…”

Solvation time of the electron in polar liquids. Water and alcohols

“…[15][16][17][18][19] Higashimura and his coworkers studied -irradiated alcohol glasses at 4 K and found a strong absorption band which peaked at infrared wavelengths. [6][7][8] This band shifts irreversibly toward blue wavelengths upon warming to 77 K. At the same time, the ESR line width increases, indicating that the cavity around the electron decreases in size and that the electron is stabilized in a deeper trap.6-8 Pulse radiolysis of alcoholic glasses and liquids shows that the disappearance of the infrared absorption is accompanied concurrently by the appearance of the absorption band of e90i-.9-14 In addition to these experimental observations, theoretical calculations also support the concept of a partially stabilized electron, et-. In ethanol, Fueki et al20 predicted an optical absorption shift due to dipole orientation of solvent molecules around the electron; this shift was at least 70% of the observed value.…”

Very low temperature pulse radiolysis. Protiated and perdeuterated methanol glasses at 6 K

“…These kinetic experiments were repeated at a reduced (by approximately 50% with a neutral density filter) light a The errors are standard deviations. 6 This wavelength could not be investigated because CH3OH absorbs strongly here. intensity at 653 and 800 nm26 for both CH30H and CD30D at 6 K. No significant effect upon either the rate of decay of the transient absorption or the percentage of the absorption observed 100 ns after the beginning of the electron pulse which is the residual absorption was found.…”