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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 first 517 days after the discovery of supernova (SN) 1999em were sampled from 30 optical spectra and 49 photometric epochs and the distance to SN 1999em was derived through the expanding photosphere method.
Abstract: We present 30 optical spectra and 49 photometric epochs sampling the first 517 days after discovery of supernova (SN) 1999em and derive its distance through the expanding photosphere method (EPM). SN 1999em is shown to be a Type II‐plateau (II‐P) event, with a photometric plateau lasting until about 100 days after explosion. We identify the dominant ions responsible for most of the absorption features seen in the optical portion of the spectrum during the plateau phase. Using the weakest unblended absorption features to estimate photospheric velocity, we find the distance to SN 1999em to be \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} ewcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} ormalfont \selectfon...

325 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the damage tracks induced by tightly focused infrared femtosecond laser pulses in the bulk of a fused silica sample and observed two types of irreversible damage.
Abstract: We investigate experimentally and numerically the damage tracks induced by tightly focused $(\mathrm{NA}=0.5)$ infrared femtosecond laser pulses in the bulk of a fused silica sample. Two types of irreversible damage are observed. The first damage corresponds to a permanent change of refractive index without structural modifications (type I). It appears for input pulse energies beyond $0.1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{J}$. It takes the form of a narrow track extending over more than $100\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ at higher input powers. It is attributed to a change of the polarizability of the medium, following a filamentary propagation which generates an electron-hole plasma through optical field ionization. A second type of damage occurs for input pulse energies beyond $0.3\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{J}$ (type II). It takes the form of a pear-shaped structural damage associated with an electron-ion plasma triggered by avalanche. The temporal evolution of plasma absorption is studied by pump-probe experiments. For type I damage, a fast electron-hole recombination is observed. Type II damage is linked with a longer absorption.

321 citations

Journal ArticleDOI
TL;DR: In this paper, an optical absorption band at 9.6 was found to be correlated with the oxygen content in silicon, and it was found that the oxygen concentration in silicon crystals prepared by the floating zone technique in vacuum was less than 10.18$ oxygen atoms per cubic centimeter.
Abstract: An optical absorption band at 9\ensuremath{\mu} has been correlated with the oxygen content in silicon. Pulled silicon crystals were found to contain up to ${10}^{18}$ oxygen atoms per ${\mathrm{cm}}^{3}$ which seem to originate from the quartz crucible. The oxygen concentration in silicon crystals prepared by the floating zone technique in vacuum was found to be less than ${10}^{16}$ oxygen atoms per ${\mathrm{cm}}^{3}$. The 9\ensuremath{\mu} absorption due to silicon-oxygen bond stretching vibrations provides a possibility for a quantitative oxygen analysis of high sensitivity. A corresponding absorption in germanium at 11.6\ensuremath{\mu} is believed to be due to a germanium-oxygen vibration.

320 citations

Journal ArticleDOI
TL;DR: In this paper, the optical properties of high-pressure phase ZnO in NaCl and C2 Cl structures were investigated using the ab initio pseudopotential density functional method, in which the Perdew-Burke-Eruzerhof form of the generalized gradient approximation available in the CASTEP code together with plane wave basis sets for expanding the periodic electron density.
Abstract: We present a detailed investigation on optical properties of high-pressure phase ZnO in $B1$ (NaCl) and $B2$ (CsCl) structures, including dielectric function, refractive index, absorption, and electron energy-loss spectrum. Theoretical calculations are performed using the ab initio pseudopotential density functional method, in which we employ the Perdew-Burke-Eruzerhof form of the generalized gradient approximation available in the CASTEP code together with plane wave basis sets for expanding the periodic electron density. Both structures are optimized under the respective structural phase transition pressures; for the $B1$ structure it is $9\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, which has been verified to be in agreement with theory [Jaffe et al., Phys. Rev. B 62, 1660 (2000)] and experiment [Desgreniers, Phys. Rev. B 58, 14102 (1998)], while for the $B2$ structure a transition pressure of $256\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ is predicted in theory [Jaffe et al., Phys. Rev. B 62, 1660 (2000)]. We find that their electronic structures and optical properties under high pressure are quite different from those under ambient pressure.

320 citations

Journal ArticleDOI
TL;DR: Significant enhancement relative to the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of >5σ, which could possibly be due to nuclear reaction interference effects or indicate that, in an intermediate step, a neutral isosCalar particle was created.
Abstract: Electron-positron angular correlations were measured for the isovector magnetic dipole 17.6 MeV (J^{π}=1^{+}, T=1) state→ground state (J^{π}=0^{+}, T=0) and the isoscalar magnetic dipole 18.15 MeV (J^{π}=1^{+}, T=0) state→ground state transitions in ^{8}Be. Significant enhancement relative to the internal pair creation was observed at large angles in the angular correlation for the isoscalar transition with a confidence level of >5σ. This observation could possibly be due to nuclear reaction interference effects or might indicate that, in an intermediate step, a neutral isoscalar particle with a mass of 16.70±0.35(stat)±0.5(syst) MeV/c^{2} and J^{π}=1^{+} was created.

317 citations


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