Excess electrons in aqueous glasses and crystalline ice

Abstract

Experimental studies of excess electrons in aqueous glasses and crystalline ice are reviewed. Emphasis is placed on studies of the two main optical absorption bands, the well known visible band, which is similar to that of the solvated electron in water, and the IR band which has λmax [Formula: see text] 2950 nm. Under some circumstances partial conversion of the IR-absorbing species to the visible-absorbing species has been observed. Evidence indicates that the two species are due to electrons trapped in distinctly different physical environments. Two mechanisms have been proposed for the formation of the visible-absorbing electron in crystalline ice, one involving naturally occurring vacancies and the other radiation produced vacancies. Studies of the UV and visible luminescence emitted when ice at low temperature is irradiated are summarized, and the mechanisms suggested for its production are discussed briefly. The studies on excess electrons in aqueous solids seem to the authors to be highly relevant to the more recent studies of electron solvation in water which are done on a much shorter time-scale. These latter studies are reviewed briefly with the aim of elucidating the relevance.Key words: visible-absorbing electrons, IR-absorbing electrons, irradiation of aqueous glasses, irradiation of crystalline ice, electron solvation in water.

Unusual Stability of Polycyclic Aromatic Hydrocarbon Radical Cations in Amorphous Water Ices up to 120 K: Astronomical Implications

“…Pulsed radiolysis experiments of pure water ices revealed that the optical absorption due to free electrons in water ice decay on the timescale of a few nanoseconds to a few microseconds. The lower the temperature, the longer the lifetime of the free electrons in this range (Gillis & Quickenden 2001). Thus, under our experimental conditions of long-term UV photolysis followed by slow spectral scanning we would expect that there would be no free electrons present in these ices at 20 K. Electrons would have more than ample time to become attached to H 2 O or OH within the ice, forming trapped H 2 O À or OH À negative ions (anions).…”

Comparison of the effects of UV, H2O2/UV and γ-irradiation processes on frozen and liquid water solutions of monochlorophenols

“…Some of the photoproducts were isolated from irradiated samples by column chromatography for analytical purposes. The structures of all the products identified [chlorobenzenediols (3)(4)(5), pyrocatechol (6), hydroquinone (7), phenol (8), chlorobiphenyldiols (9)(10)(11), and dichlorobiphenyldiols (12)] are shown below. Authentic analytical standards of 3-8 were purchased, compounds 9-11 were synthesised, 23 and photosolvolysis products obtained by irradiation of liquid samples were analysed according to our previous work.…”

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Ultrafast Dynamics of Electron Localization and Solvation in Ice Layers on Cu(111)

“…Up to now, most studies have focused on the solvation dynamics in the liquid phase, but very little is known about the initial stages of electron transfer and solvation of excess electrons in supercooled water and ice [10]. However, this knowledge is important for such diverse areas like astrophysics, environmental science, and radiation chemistry.…”