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Absorption (logic)

About: Absorption (logic) is a research topic. Over the lifetime, 5733 publications have been published within this topic receiving 236302 citations.


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TL;DR: In this article, single crystals of MgO have been additively colored by heating them in Mg vapor at temperatures from 1600 to 1800\ifmmode^\circ\else\text degree\fi{}C and pressures up to 4000 Torr.
Abstract: Single crystals of MgO have been additively colored by heating them in Mg vapor at temperatures from 1600 to 1800\ifmmode^\circ\else\textdegree\fi{}C and pressures up to 4000 Torr. The ${F}^{+}$ and ${F}^{\ensuremath{'}}$ optical absorption bands (due to anion vacancies containing one and two electrons, respectively) were observed to be extremely similar but distinguishable, and were observed at liquid-nitrogen temperature to peak at 4.96 and 5.03 eV, respectively. The oscillator strength for the ${F}^{\ensuremath{'}}$ center is estimated to be 0.70\ifmmode\pm\else\textpm\fi{}0.05. A photoconversion process ${F}^{+}\ensuremath{\leftrightarrow}{F}^{\ensuremath{'}}$ was studied. The luminescence bands for these centers were observed at 3.1 and 2.4 eV, respectively. The density of ${F}^{\ensuremath{'}}$ centers ${N}_{{F}^{\ensuremath{'}}}$ produced by the additive coloring process was observed to be related to the density of atoms in the vapor ${N}_{\mathrm{Mg}}$ by the equation ${N}_{{F}^{\ensuremath{'}}}=1270{N}_{\mathrm{Mg}}{e}^{\ensuremath{-}\frac{Q}{\mathrm{kT}}}$, where $Q=1.53$ eV. The temperature dependence of these two bands was measured and is discussed.

162 citations

Journal ArticleDOI
TL;DR: In this article, the established relation between isomer shifts and ionic states of Fe were further confirmed by measurements on several other mixed oxides and several other oxides containing iron, and the results were discussed in conjunction with their magnetic properties.
Abstract: M\"ossbauer absorption by ${\mathrm{Fe}}^{57}$ was used to study isomer shift, quadrupole splitting, and hyperfine fields in several oxides containing iron. The established relations between isomer shifts and ionic states of Fe were further confirmed by measurements on ${\mathrm{Fe}}^{2+}$${\mathrm{Ti}}_{2}$${\mathrm{O}}_{5}$, ${\mathrm{Fe}}_{2}^{3+}$Ti${\mathrm{O}}_{5}$ and several other mixed oxides. By utilizing this relation, in turn, to identify the ionic states when these are in doubt, it has been found that ${(\mathrm{F}\mathrm{e},\mathrm{V})}_{2}$${\mathrm{O}}_{3}$ incorporates the cation pair ${\mathrm{Fe}}^{3+}$ - ${\mathrm{V}}^{3+}$, rather than ${\mathrm{Fe}}^{2+}$ - ${\mathrm{V}}^{4+}$, and that "SrFe${\mathrm{O}}_{3}$" contains ${\mathrm{Fe}}^{4+}$ and ${\mathrm{Fe}}^{3+}$ in the ratio of 3:1. A well-defined quadrupole splitting was observed in ${\mathrm{Fe}}_{1\ensuremath{-}x}\mathrm{O}$ and in a number of the solid solutions (Fe,Mg)O, although their over-all symmetry is cubic. This is explained by the assumption of local asymmetry at the Fe nuclei caused either by vacancies or foreign ions. Hyperfine fields at the ${\mathrm{Fe}}^{3+}$ nuclei in ${(\mathrm{F}\mathrm{e},\mathrm{C}\mathrm{r})}_{2}$${\mathrm{O}}_{3}$, ${(\mathrm{F}\mathrm{e},\mathrm{V})}_{2}$${\mathrm{O}}_{3}$, and ${(\mathrm{F}\mathrm{e},\mathrm{A}\mathrm{l})}_{2}$${\mathrm{O}}_{3}$ have values between 520 and 540 koe when extrapolated to 0\ifmmode^\circ\else\textdegree\fi{}K, and the results are discussed in conjunction with their magnetic properties.

161 citations

Journal ArticleDOI
TL;DR: In this paper, the energy extent of the type-II multiple-scattering (MS) regime was determined by making a comparison between the Mn K-edge absorption of (${\mathrm{MnO}}_{4}$${) and [Mn${H}}_{2}$O${)}_{6}$ ] 2+}$ complexes in aqueous solution.
Abstract: By making a comparison between the Mn K-edge absorption of (${\mathrm{MnO}}_{4}$${)}^{\mathrm{\ensuremath{-}}}$ and [Mn(${\mathrm{H}}_{2}$O${)}_{6}$${]}^{2+}$ complexes in aqueous solution we obtain an experimental determination of the energy extent of the type-II multiple-scattering (MS) regime that is substantially wider than expected. Theoretical calculations based on the MS formalism support this conclusion. We also recognize three energy regions in the absorption spectra of these complexes: a full MS region, where numerous or an infinite number of MS paths of high order contribute (depending on whether the MS series converges or not), an intermediate MS region, where only a few MS paths of low order are relevant, and a single-scattering region where the photoelectron is backscattered only once by the ligands [extended x-ray-absorption fine-structure (EXAFS) regime]. Theoretical considerations show that this must be a general situation in x-ray-absorption spectra and opens the way to a unified scheme for their interpretation. The energy extent of the three regions is obviously system dependent. We also show how to generalize to MS contributions the usual EXAFS analysis using curved-wave propagators and indicate how to extract geometrical information from the spectra of the two clusters investigated. In particular the method is used to derive the Mn---O---O---Mn path length in the (${\mathrm{MnO}}_{4}$${)}^{\mathrm{\ensuremath{-}}}$ complex.

160 citations

Journal ArticleDOI
TL;DR: In this paper, a series of synthetic fused silicas of diverse OH contents was subjected to 100-keV x irradiations at 77 K and investigated by electron-spin-resonance techniques at \ensuremath{\sim}110 K or higher temperatures.
Abstract: A series of synthetic fused silicas of diverse OH contents was subjected to 100-keV x irradiations at 77 K and investigated by electron-spin-resonance techniques at \ensuremath{\sim}110 K or higher temperatures. Spectra were recorded at X-band frequencies (\ensuremath{\sim}9.2--9.3 GHz) both as the first derivative of absorption and in the high-power second-harmonic mode in order to bring out features not fully accessible by using one of these methods alone. In addition to the previously known ${E}_{\ensuremath{\alpha}}^{\mathcal{'}}$, ${E}_{\ensuremath{\gamma}}^{\mathcal{'}}$, and oxygen-associated hole centers, three new defects were detected and characterized by computer line-shape simulation methods. These were atomic chlorine, a delocalized E' center (denoted ${E}_{\ensuremath{\delta}}^{\mathcal{'}}$), and the first biradical to be reported in a-${\mathrm{SiO}}_{2}$. A sample-to-sample correlation of the radiation yields of these three new centers has been noted, leading to the suggestion that all three find their origins in specific chlorine-decorated precursor sites in the unirradiated glasses. Although significant chlorine impurities (g100 ppm) may be ubiquitous in both type-III (high OH) and type-IV (low OH) fused silicas, the occurrence of chlorine-associated radiation-induced defects appears to be anticorrelated with the OH contents of the materials. Some possible technological implications of these findings are discussed.

159 citations

Journal ArticleDOI
TL;DR: In this article, the intrinsic optical-absorption-coefficient data for undoped indium phosphide at 6, 20, and 77\ifmmode^\circ\else\text degree\fi{}K were analyzed.
Abstract: Sharp peaks due to exciton formation have been observed in the intrinsic optical-absorption-coefficient data for undoped indium phosphide at 6, 20, and 77\ifmmode^\circ\else\textdegree\fi{}K. At 298\ifmmode^\circ\else\textdegree\fi{}K, the absorption data do not show a peak, because of thermal broadening. Low-temperature photoluminescence data obtained on the same InP used for absorption data exhibited an exciton emission peak at the same energy as the absorption peak and confirm the earlier identification of the emission line due to Turner and Pettit. At 6 and 77\ifmmode^\circ\else\textdegree\fi{}K, the exciton peak energies are 1.416 and 1.409 eV, respectively. From the absorption data, the exciton binding energy at both temperatures is 0.0040 eV. The temperature dependence of the gap in the linear region above 100\ifmmode^\circ\else\textdegree\fi{}K is -2.9\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$eV/\ifmmode^\circ\else\textdegree\fi{}K, in sharp disagreement with the earlier value of Oswald.

158 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2021290
2020249
2019220
2018230
2017162
2016163