Absorption (logic)

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

L-edge x-ray-absorption systematics of the noble metals Rh, Pd, and Ag and the main-group metals In and Sn: A study of the unoccupied density of states in 4d elements.

Abstract: X-ray-absorption L-edge spectra have been obtained for the noble metals Rh, Pd, and Ag and the main-group metals In and Sn. The systematics derived from these spectra reveal that (a) the x-ray-absorption near-edge structure (XANES) is primarily related to the density of states in these systems, (b) the energy distribution of the states above the Fermi level in noble metals is qualitatively consistent with the general band-theory description and semiquantitatively in agreement with the single-particle theory of M\"uller, Jensen, and Wilkins, and (c) the ${L}_{\mathrm{I}\mathrm{I},\mathrm{I}\mathrm{I}\mathrm{I}}$ ``white-line'' intensity ratio depends on the distribution of the ${d}_{5/2}$ and ${d}_{3/2}$ population above the Fermi level and this distribution deviates significantly from the statistical distribution when the d band of the metal is nearly full. The applicability of XANES in the investigation of the charge-distribution systematics in 4d elements is discussed.

Constraints on low-mass, relic dark matter candidates from a surface-operated SuperCDMS single-charge sensitive detector

Abstract: This article presents an analysis and the resulting limits on light dark matter inelastically scattering off of electrons, and on dark photon and axion-like particle absorption, using a second-generation SuperCDMS high-voltage eV-resolution detector. The 0.93 gram Si detector achieved a 3 eV phonon energy resolution; for a detector bias of 100 V, this corresponds to a charge resolution of 3% of a single electron-hole pair. The energy spectrum is reported from a blind analysis with 1.2 gram-days of exposure acquired in an above-ground laboratory. With charge carrier trapping and impact ionization effects incorporated into the dark matter signal models, the dark matter-electron cross section $\bar{\sigma}_{e}$ is constrained for dark matter masses from 0.5--$10^{4} $MeV$/c^{2}$; in the mass range from 1.2--50 eV$/c^{2}$ the dark photon kinetic mixing parameter $\varepsilon$ and the axioelectric coupling constant $g_{ae}$ are constrained. The minimum 90% confidence-level upper limits within the above mentioned mass ranges are $\bar{\sigma}_{e}\,=\,8.7\times10^{-34}$ cm$^{2}$, $\varepsilon\,=\,3.3\times10^{-14}$, and $g_{ae}\,=\,1.0\times10^{-9}$.

Absorption and Fluorescence of Sm 2 + in Ca F 2 , Sr F 2 , and Ba F 2

Abstract: The absorption and fluorescence of the ${\mathrm{Sm}}^{2+}$ ion have been studied for three host lattices, Ca${\mathrm{F}}_{2}$, Sr${\mathrm{F}}_{2}$, and Ba${\mathrm{F}}_{2}$. Measurements of intensity, linewidth, quantum efficiency, and Zeeman splitting are reported. Energy levels belonging to the $4f$ shell have been identified, and a preliminary analysis of the $4f\ensuremath{\rightarrow}5d$ transitions is presented.

Electronic resonance enhancement of coherent anti-Stokes Raman scattering

Abstract: We analyze the enhancement of the coherent anti-Stokes Raman-scattering (CARS) susceptibility when the frequencies of the waves involved are tuned into resonance with discrete and continuum one-photon absorptions, and discuss the applications. We first derive the expression for the susceptibility by means of the usual iterative treatment of density-matrix perturbations. We then show that this derivation can be done in a straightforward manner by means of a time-ordered diagrammatic representation, which brings novel physical insight into CARS mechanisms. This representation can also be used to analyze the transient behavior of CARS as the pump fields are turned on and off. In addition, we discuss resonant CARS spectroscopy in the gas phase. The spectrum is composed of the expected enhanced Raman lines and also of double-electronic-resonance lines. All these lines occur as doublets. We derive their relative intensities based on detunings, collisional broadening, Franck-Condon overlap integrals, and rotational transition moments. The line contours are predicted by representing the susceptibility in the complex plane. The problems arising from saturation and the optical Stark effect are also considered; all should be small below pump densities of 100 MW/${\mathrm{cm}}^{2}$ in gas mixtures near STP. Fluorescence interference is negligible, except at power densities high enough for the Stark effect to be large. Beam absorption is also negligible at STP if the resonant species' concentration is less than 1000 ppm; phase matching is then satisfied. Finally, an experimental resonant CARS spectrum of ${\mathrm{I}}_{2}$ at 1 mb in air near STP is presented and interpreted; the susceptibility is about 400 times larger than that of ${\mathrm{O}}_{2}$ off resonance and under the same thermodynamic conditions.

ALPHA-PARTICLE STOPPING CROSS SECTION IN SOLIDS FROM 400 keV TO 2 MeV.

Abstract: Stopping cross sections of $\ensuremath{\alpha}$ particles from 400 keV to 2 MeV have been measured to an accuracy of \ifmmode\pm\else\textpm\fi{}3.6 to \ifmmode\pm\else\textpm\fi{}4.9% in 17 elements (Be, C, Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ge, Pd, Ag, In, and Sn). The experimental method consists of the elastic scattering of $\ensuremath{\alpha}$ particles from a thick Ta backing onto which a thin layer of target element has been evaporated. The energy loss of $\ensuremath{\alpha}$ particles in the target film is determined by the difference in energy between $\ensuremath{\alpha}$ particles scattered from clean Ta and $\ensuremath{\alpha}$ particles scattered from Ta after having gone through the thin layer of target element. The results are compared with measurements by Porat and Ramavataram and by Gobeli and with estimates by Whaling; the discrepancies range from 1 to 20%. Structure in and a decrease of the $\ensuremath{\alpha}$-particle stopping cross section ${\ensuremath{\epsilon}}_{\ensuremath{\alpha}}$ with stopping element atomic number ${Z}_{2}$ are noticed in the region ${Z}_{2}=22\ensuremath{-}29$. This dependence is not predicted by the Bethe-Bloch formalism valid at higher velocities, nor by the Firsov or the Lindhard formalism valid at lower velocities. The oscillatory structure of ${\ensuremath{\epsilon}}_{\ensuremath{\alpha}}$ on ${Z}_{2}$ is discussed qualitatively by comparing ${\ensuremath{\epsilon}}_{\ensuremath{\alpha}}({E}_{\ensuremath{\alpha}})$ versus ${Z}_{2}$ with a Hartree-Fock-Slater potential $\ensuremath{\varphi}(r)$ versus $Z$, with ${E}_{\ensuremath{\alpha}}$ related to the radius $r$ by a velocity comparison. An empirical formula for ${\ensuremath{\epsilon}}_{\ensuremath{\alpha}}={\ensuremath{\epsilon}}_{\ensuremath{\alpha}}({E}_{\ensuremath{\alpha}}, {Z}_{2})$ has been constructed from the present measurements.