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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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Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate optical levitation of 12-ng spheres with masses ranging from 0.1 to 30 ng in high vacuum and demonstrate that the measured acceleration sensitivity improves for larger masses.
Abstract: We demonstrate optical levitation of ${\mathrm{SiO}}_{2}$ spheres with masses ranging from 0.1 to 30 ng. In high vacuum, we observe that the measured acceleration sensitivity improves for larger masses and obtain a sensitivity of $0.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\phantom{\rule{4pt}{0ex}}g/\sqrt{\mathrm{Hz}}$ for a 12-ng sphere, more than an order of magnitude better than previously reported for optically levitated masses. In addition, these techniques permit long integration times and a mean acceleration of $(\ensuremath{-}0.7\ifmmode\pm\else\textpm\fi{}2.4\phantom{\rule{0.16em}{0ex}}[\text{stat}]\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.16em}{0ex}}[\text{syst}])\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}\phantom{\rule{0.16em}{0ex}}g$ is measured in $1.4\ifmmode\times\else\texttimes\fi{}{10}^{4}$ s. Spheres larger than 10 ng are found to lose mass in high vacuum where heating due to absorption of the trapping laser dominates radiative cooling. This absorption constrains the maximum size of spheres that can be levitated and allows a measurement of the absorption of the trapping light for the commercially available spheres tested here. Spheres consisting of material with lower absorption may allow larger objects to be optically levitated in high vacuum.

115 citations

Journal ArticleDOI
TL;DR: The first quantitative analysis of the Fe K-edge polarized x-ray absorption near edge structure of the iron protein carbonmonoxy-myoglobin single crystal and of its cryogenic photoproduct Mb(*)CO is reported.
Abstract: We report the first quantitative analysis of the Fe K-edge polarized x-ray absorption near edge structure of the iron protein carbonmonoxy-myoglobin (MbCO) single crystal and of its cryogenic photoproduct ${\mathrm{Mb}}^{*}\mathrm{CO}$. The CO-Fe-heme local structure has been determined using a novel fitting procedure based on the full multiple scattering approach. The extracted local structure of ${\mathrm{Mb}}^{*}\mathrm{CO}$ includes a Fe-CO distance of $(3.08\ifmmode\pm\else\textpm\fi{}0.07)\phantom{\rule{0ex}{0ex}}\AA{}$, with a tilting angle between the heme normal and the Fe-C vector of $(37\ifmmode\pm\else\textpm\fi{}7)\ifmmode^\circ\else\textdegree\fi{}$, and a bending angle between the Fe-C vector and the C-O bond of $(31\ifmmode\pm\else\textpm\fi{}5)\ifmmode^\circ\else\textdegree\fi{}$.

115 citations

Journal ArticleDOI
TL;DR: In this article, the structural and magnetic properties of reactive magnetron sputtering films were studied based on x-ray absorption, and it was shown that the Co atoms are in a divalent state and in tetrahedral coordination, thus substituting Zn in the wurtzite type structure of ZnO.
Abstract: Using the spectroscopies based on x-ray absorption, we have studied the structural and magnetic properties of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}\mathrm{O}$ films ($x=0.1$ and 0.25) produced by reactive magnetron sputtering. These films show ferromagnetism with a Curie temperature ${T}_{C}$ above room temperature in bulk magnetization measurements. Our results show that the Co atoms are in a divalent state and in tetrahedral coordination, thus substituting Zn in the wurtzite-type structure of ZnO. However, x-ray magnetic circular dichroism at the $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}{L}_{2,3}$ edges reveals that the $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}3d$ sublattice is paramagnetic at all temperatures down to $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, both at the surface and in the bulk of the films. The $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}3d$ magnetic moment at room temperature is considerably smaller than that inferred from bulk magnetization measurements, suggesting that the $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}3d$ electrons are not directly at the origin of the observed ferromagnetism.

115 citations

Journal ArticleDOI
J. Pankove1
TL;DR: In this article, it was shown that the spontaneous emission efficiency of GaAs 1-x P x injection lasers varies exponentially with the temperature T: θ 1 and θ 2 are usually nearly equal and range between 50 and 110°K.
Abstract: It is found that in GaAs 1-x P x injection lasers both the spontaneous emission efficiency η and the laser threshold j vary exponentially with the temperature T: \eta = \eta_{0} \exp(-T/\theta_{1}) and j = j_{0} \exp(T/\theta_{2}) . θ 1 and θ 2 are usually nearly equal and range between 50 and 110°K. The behavior of the external efficiency is correlated with the temperature dependence of the absorption along the propagation path of the radiation: as the temperature increases, the exponential absorption edge shifts to lower energies faster than the emission peak. The difference between the two shifts is nearly linear with temperature. The effect of self-absorption on external efficiency was tested by measuring the light emitted transversely to the p-n junction through a layer of constant thickness. With such a geometry, it is shown that the efficiency should vary as \exp [-A \exp (T/\theta)] . The experiment agrees with this prediction.

115 citations

Journal ArticleDOI
TL;DR: In this paper, the optical-spectroscopic properties of alexandrite (BeAl) and O(O(O)) crystals were studied by different laser spectroscopy techniques and the temperature dependences of the fluorescence lifetimes and widths of the zero-phonon lines were found.
Abstract: Details of the optical-spectroscopic properties of alexandrite (${\mathrm{BeAl}}_{2}$${\mathrm{O}}_{4}$:${\mathrm{Cr}}^{3+}$) crystals were studied by different laser-spectroscopy techniques. The temperature dependences of the fluorescence lifetimes and widths of the zero-phonon lines were found to be quite different for ${\mathrm{Cr}}^{3+}$ ions in the mirror and inversion crystal-field sites. The results indicate that direct phonon-absorption processes dominate both thermal line broadening and lifetime quenching for ions in the mirror sites while phonon-scattering processes dominate the line broadening of inversion-site ions and leave their lifetime independent of temperature. Tunable-dye-laser site-selection methods were used to obtain the excitation spectra of the ${\mathrm{Cr}}^{3+}$ ions in inversion sites at low temperature and to identify six types of exchange-coupled pairs of ${\mathrm{Cr}}^{3+}$ ions in the lattice. Time-resolved site-selection spectroscopy was used to monitor the energy transfer between ${\mathrm{Cr}}^{3+}$ ions in mirror and inversion sites at both low and high temperature. Finally, high-power, picosecond pulse excitation was used to produce two-photon absorption, and the resulting emission spectrum was found to exhibit a new fluorescence band in the 400-nm spectral region.

115 citations


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