Pulse radiolysis of deuterated aqueous LiCl glasses. Dependence of the yields and rates of reaction of visible and infrared absorbing trapped electrons on LiCl concentration

Self Cite

. Can. J. Chem. 61, 189 (1983) The yield and reaction kinetics of trapped electrons, e, and e,,, in several ethylene glycol/DZO glasses have been studied from 6-72 K by pulse radiolysis. An increased DZO concentration is believed to increase the concentration of IR-traps thereby leading to a greater G(e,) and to decrease the concentration of VIS-traps thereby increasing the stability of e,. The yield and stability of e, are also increased by lowering the temperature. A redetermination of ~(e.;) (1.3 x lo4 M cm-' at 1800 nm) confirms earlier values. ZHENNAN WU, NORMAN V. KLASSEN. HUGH A. GILLIS et GEORGE G. TEATHER. Can. J. Chem. 61, 189 (1983).--Le rendement et les cinCtiques des Clectrons piegCs, ci, ct eVi,, dans quelques verrcs de glycol d'tthyl&ne/DZO ont Ct C CtudiCs de 6-72 K par radiolyse pulsCe. Une augmentation en concentration de D'O augmente la concentration des pikges-IR, qui entraine une valeur plus elevCe pour G(e,i), et baisse la concentration des pikges-VIS augmentant la stabilitC de e,. Le rendement et la stabilitC de e, sont aussi augmente par une baisse de tempkrature. Une redktermination de ~( e , ) (1.3 X 10" M-' cm-' a 1800 nm) confirme la valeur prCcCdente. IntroductionAqueous ethylene glycol glass has proven to be a useful matrix in which to study the behaviour of infrared-absorbing trapped electrons, e, , and visible-absorbing trapped electrons, e,, (1 -7). The pulse radiolysis of pure ethylene glycol (EG) glass, even at 6 K , shows no evidence of e, whereas both e, and e,, are produced in 50/50 (vol/vol) EG/D20 and EG/H20 glasses (3,4). Thus the presence of water permits the production of e i .In publications from this laboratory, pulse radiolysis experiments have been interpreted as indicating that e, and e,, are electrons trapped in two distinctly different molecular environments both in certain aqueous glasses (1 -4, 8, 9) and in crystalline ice (10, 1 l), although the conversion of e.; into e,, is readily observable in some aqueous glasses (1, 8, 12) including aqueous EG glasses (I). Dolivo and Kevan (13), on the other hand, have argued that the essential difference between the two types of electron is that e. : has a first solvation shell of water molecules which are not at equilibrium, whereas the water molecules immediately adjacent to e,, are at equilibrium. The present results continue to favour two distinctly different molecular environments for e, and e,,.In this study, the pulse radiolysis of EG/D20 glasses of varied composition provides new insight into the production and decay of e, and e,, and the interdependence of the two species. A redetermination of ~( e , ) was made to insure the reliability of the calculated values of G(e,) and G(e,,).

Section: Discussionmentioning

confidence: 88%

A pulse radiolysis study of trapped electrons in aqueous ethylene glycol glasses

Wu¹,

Klassen²,

Gillis³

et al. 1983

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“…Most of the experimental techniques used in this work have deuterium substitution' One expects find erir been described earlier (1)(2)(3)(4). The light detector for h 2 900 nm also in ~rotiated systems but heretofore the ~osslbll-was a Barnes A-100 room temperature InAs photodiode.…”

Section: Introductionmentioning

confidence: 92%

“…In pulse radiolysis studies of some deuterated They that lo% by in D2° aqueous solids at low temperature, two well sepa-ice Was sufficient to suppress the appearance of rated absorption bands due to excess electrons are e-i,. seen (1)(2)(3)(4). The better known of these, ePvis, has an In this work ePir was looked for in several prooptical absorption with a maximum around 650 nm.…”

Section: Introductionmentioning

confidence: 99%

Localized excess electrons in H₂O glasses and ice

Trudel¹,

Gillis²,

Klassen³

et al. 1981

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. Can. J. Chem. 59, 1235Chem. 59, (1981. The yields and decay rates of two types of localized excess electrons, absorbing in the visible (e-,,,) and in the infrared (e-,,), have been compared in four pulse-irradiated H,O glasses and their D,O analogues, and in irradiated H,O and D 2 0 ice crystals, all at 73 K. If it is assumed that extinction coefficients of e-,,, and e-,, at 650 nm and 1800 nm, respectively, are independent of isotopic substitution for both glasses and ice, the G's for both types of localized electrons are lower in all the H,O solids studied than in the corresponding D,O solids. The largest effect of isotopic substitution was found in the lifetime of e-,,, in the crystal; at 73 K the inital half-life for decay of e-,,, is approximately 14 times longer in D 2 0 than in H 2 0 ice. Even at 6 K the decay of e-,,, in H 2 0 ice is very rapid with an initial half-life of about 75 ns. [Traduit par le journal]

“…Both are unstable and decay with the same kinetics, albeit with more than four orders of magnitude difference in the lifetimes. There are some indications that the yield and lifetime of the 'red wing' change with the amount of electrolyte added to the glass (23) and a study of this dependence, as was done with the 'infrared band' (12,23), should provide some insight into the nature of this trap.…”

Section: Conclusioi7smentioning

confidence: 99%

“…Frozen aqueous LiCl glass was chosen as the medium for this study because its radiation chemistry has been thoroughly investigated (ll), it accommodates the infrared-absorbing electron state (e,,-) (12,13), a range of electrolyte concentrations can be used (10,12), and its steady-state (14) and time-…”

Section: Introductionmentioning

confidence: 99%

Partial deconvolution of the absorption spectrum of trapped electrons in 15 M LiCl aqueous glasses at 77 K

Nguyen¹

1979

TUAN QUOC NGUYEN. Can. J. Chem. 57, 1758Chem. 57, (1979. Evidence is presented for the composite nature of the solvated (or trapped) electron absorption band in LiCl aqueous glass at 77 K. It is shown that the overall visible absorption spectrum can be deconvoluted into a homogeneously-bleachable 'green' band and a heterogeneously-bleachable 'red' band, whose relative magnitude and absorption band-maxima change with the concentration of electrolyte. From the combined results of time-resolved and steady-state photobleaching experiments, it is concluded that at least two unstable bands are formed during photobleaching (with smaller lifetimes for the band lying further towards the infrared) which then reconverted into the 'green' band with over 40% efficiency.TUAN QUOC NGUYEN. Can. J. Chem. 57, 1758Chem. 57, (1979. Les resultats montrent que le spectre d'absorption de l'electron solvate (ou piege) dans les verres aqueux contenant du LiCl a 77 K est la resultante de plusieurs bandes d'absorption distinctes. Par photoblanchiment fractionnt, il a ete possible de dCconvolutionner partiellement cette bande d'absorption en deux composants: une bande "verte" qui se comporte de maniere homogene sous photoblanchiment, et une bande "rouge" non-homogene. Le rapport des intensites et la position de chacun des deux pics d'absorption changent avec la concentration en electrolyte. Les resultats obtenus par photoblanchiment rCsolu dans le temps et ceux par photoblanchiment stationnaire ont permis de conclure qu'au moins deux bandes instables sont ainsi formees par photoblanchiment (avec une duree de vie d'autant plus courte que leur absorption se trouve loin dans l'infrarouge), qui se retransforment ensuite en bande "verte" avec un rendement superieur a 40%.