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We report the first observations of optically induced electron spin resonance signals in doped and undoped amorphous silicon. We also report the observation of equilibrium surface or interface spin densities ~ 1013cm?2 and volume spin densities ~ 6 × 1015 cm?3. The small number of spins observed in equilibrium compared to the large optically induced spin density shows that most electrons are spin paired in equilibrium. We conclude that this implies a very small mean effective correlation energy, U ~ kT. 相似文献
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Solomon L. Schwebel 《International Journal of Theoretical Physics》1970,3(5):347-353
The appearance of retarded and advanced solutions to the wave equation and thead hoc choice of one of them in preference to the other has led to the claim that electromagnetic theory is incomplete. It is contended that some other condition outside that theory must be invoked in order to make a meaningful physical choice. However, both a physical and mathematical analysis show, that, in fact, both retarded and advanced solutions are necessary and that the rejection of the advanced type of solution is not valid; that its rejection is based on an ambiguous mathematical technique and a faulty physical interpretation. A unique form for the Green's function is obtained which is related to all other types of Green's functions by the appropriate adjunction of solutions to the homogeneous equation. 相似文献
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Yoon J Mirica LM Stack TD Solomon EI 《Journal of the American Chemical Society》2005,127(39):13680-13693
Multicopper oxidases catalyze the 4e- reduction of O2 to H2O. Reaction of the fully reduced enzyme with O2 produces the native intermediate (NI) that consists of four oxidized Cu centers, three of which form a trinuclear cluster site, all bridged by the product of full O2 reduction. The most characteristic feature of NI is the intense magnetic circular dichroism pseudo-A feature (a pair of temperature-dependent C-terms with opposite signs) associated with O --> Cu(II) ligand-to-metal charge transfer (LMCT) that derives from the strong Cu-O bonds in the trinuclear site. In this study, the two most plausible Cu-O structures of the trinuclear site, the tris-mu2-hydroxy-bridged and the mu3-oxo-bridged structures, are evaluated through spectroscopic and electronic structure studies on relevant model complexes, TrisOH and mu3O. It is found that the two components of a pseudo-A-term for TrisOH are associated with LMCT to the same Cu that are coupled by a metal-centered excited-state spin-orbit coupling (SOC), whereas for mu3O they are associated with LMCT to different Cu centers that are coupled by oxo-centered excited state SOC. Based on this analysis of the two candidate models, only the mu3-oxo-bridged structure is consistent with the spectroscopic properties of NI. The Cu-O sigma-bonds in the mu3-oxo-bridged structure would provide the thermodynamic driving force for the 4e- reduction of O2 and would allow the facile electron transfer to all Cu centers in the trinuclear cluster that is consistent with its involvement in the catalytic cycle. 相似文献
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Vanadium Kβ5 emission bands from pure metal and nitrides VN and VN0,82are investigated with an electron microprobe by automatic data collection and computer processing. Spectra are compared with the ones described previously. Their fine structure and the effects of the chemical bond are discussed in relation to the theories proposed in literature. 相似文献