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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 paper, the authors attributed the photoabsorption spectra of rare earths to exchange interaction, which splits the $4{d}^{9}4{f}^{N+1} configuration and raises some multiplets by 20 eV.
Abstract: Broad peaks observed in the photoabsorption spectra of rare earths \ensuremath{\sim}10-20 eV above the $4d$ edge are attributed to transitions $4{d}^{10}4{f}^{N}\ensuremath{\rightarrow}4{d}^{9}4{f}^{N+1}$. Exchange interaction splits the $4{d}^{9}4{f}^{N+1}$ configuration and raises some multiplets by \ensuremath{\sim}20 eV. Autoionization to $4{d}^{9}\ensuremath{-}4{f}^{N}\ensuremath{\epsilon}f$ broadens the high levels. The interpretation extends to $p\ensuremath{\rightarrow}d$ processes observed in the absorption of synchrotron light by transition elements.

169 citations

Journal ArticleDOI
TL;DR: The x-ray-absorption near-edge structure (XANES) at the Fe$K$ edge has been measured and interpreted by means of multiple-scattering calculations as mentioned in this paper.
Abstract: The x-ray-absorption near-edge structure (XANES) at the Fe$K$ edge of ${\mathrm{K}}_{3}$Fe${(\mathrm{CN})}_{6}$ and ${\mathrm{K}}_{4}$Fe${(\mathrm{CN})}_{6}$ has been measured and interpreted by means of multiple-scattering calculations. The theory is able to account for the XANES over a 40-eV energy range. We demonstrate that the quasidiatomic "shape resonances" arising from multiple scattering within the CN groups play an important role in the XANES and suggest that this may be a common feature of XANES of metal atoms bound to molecular groups (e.g., CO, CN,...) containing multiple bonds. The effects on the XANES of bond-length changes and distortions of the coordination geometry of the Fe${(\mathrm{CN})}_{6}$ cluster have been estimated. The different XANES spectra of ${[\mathrm{F}\mathrm{e}{(\mathrm{CN})}_{6}]}^{2+}$ and of ${[\mathrm{F}\mathrm{e}{(\mathrm{CN})}_{6}]}^{3+}$ have been interpreted in terms of charge-induced structural modifications. Comparison of XANES with extended x-ray-absorption fine-structure (EXAFS) and diffraction data shows that XANES can be used as a quantitative probe of local structure distortions which are not detected by EXAFS.

168 citations

Journal ArticleDOI
TL;DR: Big bang nucleosynthesis can provide constraints on the expansion rate at that time, limits on possible variations in Newton's constant, G, and recent measurements of the primordial deuterium abundance in quasar absorption systems now allows a new tighter constraint on G to be derived without recourse to considerations of helium or lithium abundances.
Abstract: Big bang nucleosynthesis can provide, via constraints on the expansion rate at that time, limits on possible variations in Newton's constant, $G$. The original analyses were performed before an independent measurement of the baryon-to-photon ratio from the cosmic microwave background was available. Combining this with recent measurements of the primordial deuterium abundance in quasar absorption systems now allows one to derive a new tighter constraint on $G$ without recourse to considerations of helium or lithium abundances. We find that, compared to today's value, ${G}_{0}$, ${G}_{\mathrm{BBN}}/{G}_{0}={1.01}_{\ensuremath{-}0.16}^{+0.20}$ at the $68%$ confidence level.

167 citations

Journal ArticleDOI
TL;DR: In this paper, an infrared magneto-optical study of the highly thermoelectric narrow-gap semiconductor was performed in magnetic fields oriented both parallel and perpendicular to the trigonal axis of this layered material and supplemented with UV-visible ellipsometry to obtain the optical conductivity.
Abstract: We present an infrared magneto-optical study of the highly thermoelectric narrow-gap semiconductor ${\text{Bi}}_{2}{\text{Se}}_{3}$. Far-infrared and midinfrared (IR) reflectance and transmission measurements have been performed in magnetic fields oriented both parallel and perpendicular to the trigonal $c$ axis of this layered material and supplemented with UV-visible ellipsometry to obtain the optical conductivity ${\ensuremath{\sigma}}_{1}(\ensuremath{\omega})$. With lowering of temperature we observe narrowing of the Drude conductivity due to reduced quasiparticle scattering, as well as an increase in the absorption edge due to direct electronic transitions. Magnetic fields $H\ensuremath{\parallel}c$ dramatically renormalize and asymmetrically broaden the strongest far-IR optical phonon, indicating interaction of the phonon with the continuum free-carrier spectrum and significant magnetoelectric coupling. For the perpendicular field orientation, electronic absorption is enhanced, and the plasma edge is slightly shifted to higher energies. In both cases the direct transition energy is softened in magnetic field.

167 citations

Journal ArticleDOI
TL;DR: Optical absorption, refractive index, dielectric constant, nonlinear optical coefficients, and linear electro-optic coefficients are reported for single-domain crystals of orthorhombic barium sodium niobate as mentioned in this paper.
Abstract: Optical absorption, refractive index, dielectric constant, nonlinear optical coefficients, and linear electro-optic coefficients are reported for single-domain crystals of ${\mathrm{Ba}}_{2}$Na${\mathrm{Nb}}_{5}$${\mathrm{O}}_{15}$ between room temperature and the Curie temperature. Orthorhombic ($\mathrm{mm}2$) barium sodium niobate, a filled tungsten-bronze structure, is stable to intense laser radiation, and its phasematchable nonlinear coefficients are 3 times those of LiNb${\mathrm{O}}_{3}$ and LiI${\mathrm{O}}_{3}$. For the 1.064-\ensuremath{\mu}m laser fundamental, the observed phase-match temperatures and the angular half-widths of the phase-matched second-harmonic intensity due to the coefficients ${d}_{31}$ and ${d}_{32}$ are found to be in good agreement with the values calculated from refractive-index data. The dielectric constant and electro-optic half-wave voltage data indicate that ${\mathrm{Ba}}_{2}$Na${\mathrm{Nb}}_{5}$${\mathrm{O}}_{15}$ is a useful electro-optic modulator material. The temperature variation of the spontaneous polarization ${P}_{S}$ is deduced from the birefringence, electro-optic, nonlinear optical, and pyroelectric data. It is concluded that the ferroelectric transition in ${\mathrm{Ba}}_{2}$Na${\mathrm{Nb}}_{5}$${\mathrm{O}}_{15}$ is of the first order.

166 citations


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