“…Some degree of uncertainty in the real band gaps of the studied materials, changes in the band gap at the surface, and other factors may affect the peak position and width. The resonant character of the “H 2 yield vs band gap” dependence is consistent with an exciton transfer mechanism. ,, 9 Hydrogen radiation chemical yield vs oxide band gap for radiolysis of H 2 O molecules adsorbed on the surface of various oxides with coverage 1 ± 0.4 ML. G (H 2 ) is calculated on an electron fraction basis relative to the energy of γ rays directly absorbed by the H 2 O molecules.…”
Section: Discussionmentioning
confidence: 54%
“…The resonant character of the "H 2 yield vs band gap" dependence is consistent with an exciton transfer mechanism. 15,16,17 B. Water Molecule Dissociation.…”
Section: Discussionmentioning
confidence: 99%
“…Resonant-type dependence is suggested for the exciton transfer process. − , Exciton transfer was proposed for N 2 O radiolysis on the ZrO 2 and Al 2 O 3 surfaces at 77 K. ,− According to the Förster theory, , an exciton transfer occurs due to a weak dipole−dipole coupling in the condensed state. The donor (oxide) exciton spectrum should overlap the dissociative excitation spectrum of the acceptor (the adsorbed molecule).…”
Section: Discussionmentioning
confidence: 99%
“…12 The lifetime of thermalized electronic excitations in perfect, defect-free crystals can be long enough to provide much longer distances of migrationsup to hundreds of micrometers. 3,5,13,14 For oxides, an interfacial energy transfer was observed for radiolysis of N 2 O adsorbed on ZrO 2 and SiO 2 , 8 Al 2 O 3 , and MgO; [15][16][17][18] H 2 O adsorbed on ZrO 2 , Er 2 O 3 , and La 2 O 3 ; 19 methanol adsorbed on ZrO 2 , CaO, Al 2 O 3 , MgO, and SiO 2 ; 9 NO 3 -and azoethane adsorbed on MgO. 6,10 The mechanism for energy transfer is not well understood.…”
Section: Introductionmentioning
confidence: 99%
“…For oxides, an interfacial energy transfer was observed for radiolysis of N 2 O adsorbed on ZrO 2 and SiO 2 , Al 2 O 3 , and MgO; − H 2 O adsorbed on ZrO 2 , Er 2 O 3 , and La 2 O 3 ; methanol adsorbed on ZrO 2 , CaO, Al 2 O 3 , MgO, and SiO 2 ; NO 3 - and azoethane adsorbed on MgO. , The mechanism for energy transfer is not well understood. Three major models typically are discussed: hole-electron (or electron−hole) recombination on the adsorbed molecule, dissociative electron attachment, and resonance exciton coupling.…”
The effect of an oxide interface on 60 Co gamma radiolysis of water molecules was studied. On the basis of the molecular hydrogen yield when compared with the radiolysis of the control ampules without oxides, all the tested materials can be generally classified into three groups: I. Oxides that lower the H 2 yield (MnO 2 , Co 3 O 4 , CuO, and Fe 2 O 3 ); II. Oxides with H 2 yields that are close to G values obtained in control experiments
“…Some degree of uncertainty in the real band gaps of the studied materials, changes in the band gap at the surface, and other factors may affect the peak position and width. The resonant character of the “H 2 yield vs band gap” dependence is consistent with an exciton transfer mechanism. ,, 9 Hydrogen radiation chemical yield vs oxide band gap for radiolysis of H 2 O molecules adsorbed on the surface of various oxides with coverage 1 ± 0.4 ML. G (H 2 ) is calculated on an electron fraction basis relative to the energy of γ rays directly absorbed by the H 2 O molecules.…”
Section: Discussionmentioning
confidence: 54%
“…The resonant character of the "H 2 yield vs band gap" dependence is consistent with an exciton transfer mechanism. 15,16,17 B. Water Molecule Dissociation.…”
Section: Discussionmentioning
confidence: 99%
“…Resonant-type dependence is suggested for the exciton transfer process. − , Exciton transfer was proposed for N 2 O radiolysis on the ZrO 2 and Al 2 O 3 surfaces at 77 K. ,− According to the Förster theory, , an exciton transfer occurs due to a weak dipole−dipole coupling in the condensed state. The donor (oxide) exciton spectrum should overlap the dissociative excitation spectrum of the acceptor (the adsorbed molecule).…”
Section: Discussionmentioning
confidence: 99%
“…12 The lifetime of thermalized electronic excitations in perfect, defect-free crystals can be long enough to provide much longer distances of migrationsup to hundreds of micrometers. 3,5,13,14 For oxides, an interfacial energy transfer was observed for radiolysis of N 2 O adsorbed on ZrO 2 and SiO 2 , 8 Al 2 O 3 , and MgO; [15][16][17][18] H 2 O adsorbed on ZrO 2 , Er 2 O 3 , and La 2 O 3 ; 19 methanol adsorbed on ZrO 2 , CaO, Al 2 O 3 , MgO, and SiO 2 ; 9 NO 3 -and azoethane adsorbed on MgO. 6,10 The mechanism for energy transfer is not well understood.…”
Section: Introductionmentioning
confidence: 99%
“…For oxides, an interfacial energy transfer was observed for radiolysis of N 2 O adsorbed on ZrO 2 and SiO 2 , Al 2 O 3 , and MgO; − H 2 O adsorbed on ZrO 2 , Er 2 O 3 , and La 2 O 3 ; methanol adsorbed on ZrO 2 , CaO, Al 2 O 3 , MgO, and SiO 2 ; NO 3 - and azoethane adsorbed on MgO. , The mechanism for energy transfer is not well understood. Three major models typically are discussed: hole-electron (or electron−hole) recombination on the adsorbed molecule, dissociative electron attachment, and resonance exciton coupling.…”
The effect of an oxide interface on 60 Co gamma radiolysis of water molecules was studied. On the basis of the molecular hydrogen yield when compared with the radiolysis of the control ampules without oxides, all the tested materials can be generally classified into three groups: I. Oxides that lower the H 2 yield (MnO 2 , Co 3 O 4 , CuO, and Fe 2 O 3 ); II. Oxides with H 2 yields that are close to G values obtained in control experiments
The postulated roles of clays and other minerals in chemical evolution and the origin of life are reconsidered in terms of the interaction of these minerals with penetrating sources of energy such as ionizing radiation and mechanical stress. This interaction, including such facets as excitation, degradation, storage, and transfer, is considered here with regard to its profound potential for altering the capabilities of minerals to serve both as substrates for prebiological chemistry and as inorganic prototypic life forms. The interaction of minerals and energy in relationship to surface chemistry is discussed in terms of the spectroscopic properties of minerals, the interaction of energy with condensed phases, some commonly accepted concepts of heterogeneous catalysis in the absence of electronic energy inputs, and some commonly accepted and novel means by which surface activity might be enhanced in the presence of energy inputs. An estimation is made of the potential contribution of two poorly characterized prebiotic energy sources, natural radioactive decay and triboelectric energy. These estimates place a conservative lower limit on their prebiotic abundance. Also some special properties of these energy sources, relative to solar energy, are pointed out which might give them particular suitability for driving reactions occurring under geological conditions. Skeletal support for this broadly defined framework of demonstrated and potential relationships between minerals, electronic excitation, and surface reactivity, as applied to chemical evolution, is provided from the results of our studies on 1/1 clays. We have discovered and partially characterized a number of novel luminescent properties of these clays, that indicate energy storage and transfer processes in clays. These luminescent properties are interpreted in relationship to the electron spin resonance phenomena, to provide a basis for estimating the potential significance of energy storage and transduction in monitoring or driving clay surface chemistry. Consideration of the electronic structure of abundant minerals in terms of band theory and localized defect centers provides a predictive theoretical framework from which to rationalize the capacity of these materials to store and transduce energy. The bulk crystal is seen as a collecting antenna for electronic energy, with the defect centers serving as storage sites. The clay properties produced by isomorphic substitution appear to be intimately associated with all of the life-mimetic chemical processes that have been attributed to clays.(ABSTRACT TRUNCATED AT 400 WORDS)
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