Absorption (logic)

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

Question of Gauge: Nonresonant Two-Photon Absorption

Abstract: The transition probability per unit time for nonresonant two-photon absorption from the $1s$ to the $2s$ state of atomic hydrogen is obtained analytically using both the electric-dipole interaction $\ensuremath{-}e\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}}$ and the Coulomb-gauge interaction $\ensuremath{-}(\frac{e}{m})\stackrel{\ensuremath{\rightarrow}}{\mathrm{A}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}$. The two rates are different, except in the case of resonance. In situations like this, gauge invariance can be used to show that results calculated from the $\ensuremath{-}e\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}}$ interaction are always correct.

Interpreting the near edges of O2 and O2- in alkali-metal superoxides

Abstract: Depositing alkali metal into a molecular oxygen layer dispersed on a Kr film produces alkali-metal superoxides containing the ${\mathrm{O}}_{2}^{\mathrm{\ensuremath{-}}}$ species for photoemission and near-edge study. The O K-edge spectrum of ${\mathrm{LiO}}_{2}$, ${\mathrm{KO}}_{2}$, and ${\mathrm{CsO}}_{2}$ is in good agreement with theoretical calculations for the free ${\mathrm{O}}_{2}^{\mathrm{\ensuremath{-}}}$ ion. The O K edge for the superoxide strongly resembles that observed for ${\mathrm{O}}_{2}$, which is nondissociatively adsorbed on a metal surface.

Disorder, defects, and optical absorption in a-si and a-si:h

Abstract: In this paper we present the optical properties of various structural models for $a\ensuremath{-}\mathrm{Si}$ and $a\ensuremath{-}\mathrm{S}\mathrm{i}:\mathrm{H}.$ We discuss how topological disorder, hydrogen content, and different types of defects (dangling bonds and floating bonds) influence the shape of the optical-absorption spectrum and the position of the Urbach edge. The absorption behavior is characterized by the joint density of states. The band gaps are obtained via the Tauc plot. The principal structure of the optical absorption spectrum is determined mainly by the degree of topological disorder and the amount of hydrogen. The presence of defects gives rise to tail absorption. Dangling bonds affect the optical properties more than floating bonds do.

Heat transfer in a second-order fluid over a continuous stretching surface

Abstract: The heat transfer characteristics of a second-order fluid over a continuous stretching surface with internal heat generation or absorption is analyzed. Two cases are studied, namely (i) the sheet with prescribed surface temperature (PST-case) and (ii) the sheet with prescribed wall heat flux (PHF-case). The solution and heat transfer characteristics are obtained in terms of Kummer's functions. For large values of Prandtl number a uniform approximation is given in terms of parabolic cylinder functions with a boundary layer of width\(\sqrt {{1 \mathord{\left/ {\vphantom {1 {\Pr }}} \right. \kern- ulldelimiterspace} {\Pr }}} \) in both the PST and PHF cases. It is also shown that no boundary layer type solution exists for small Prandtl number.

Temperature dependence of exchange narrowing in the one-dimensional antiferromagnet N ( C H 3 ) 4 Mn Cl 3 (TMMC)

Abstract: A quantitative analysis of the temperature and angular dependence of the exchange-narrowed EPR linewidth $\ensuremath{\Delta}H(\ensuremath{\theta},T)$ at $K$ band is presented between $40lTl300$ \ifmmode^\circ\else\textdegree\fi{}K for the one-dimensional antiferromagnet ${\mathrm{N}(\mathrm{C}{\mathrm{H}}_{3})}_{4}$Mn${\mathrm{Cl}}_{3}$ (TMMC). The $s=(\frac{5}{2})$ Mn(II) moments are treated as classical spins in order to avoid decoupling four-spin correlation functions arising from the antiferromagnetic coupling at either short or long time. The proper treatment of spin correlations accounts for the $T$ dependence of $\ensuremath{\Delta}H$ and provides a 20% correction to the high-$T$ limit even at 300\ifmmode^\circ\else\textdegree\fi{}K. No adjustable parameters are needed for a quantitative fit at $\ensuremath{\theta}=54\ifmmode^\circ\else\textdegree\fi{}$ (between the applied field and the chain axis), where the absorption is Lorentzian. The dominant broadening arising from intrachain dipolar interactions ${\mathcal{H}}^{\ensuremath{'}}$ limits diffusive behavior and leads to an adjustable parameter which controls the magnitude of $\ensuremath{\Delta}H(0,T)$ and the non-Lorentzian profile at $\ensuremath{\theta}=0$. The increasing importance of short-time effects and the decreasing importance of diffusive contributions to $\ensuremath{\Delta}H$ are quantitatively illustrated at $T=77$ \ifmmode^\circ\else\textdegree\fi{}K. This trend continues to lower $T$, although the $T=20$ \ifmmode^\circ\else\textdegree\fi{}K and $T=4.2$ \ifmmode^\circ\else\textdegree\fi{}K data cannot be treated by the present model of only including spin correlations due to isotropic exchange. The angular anisotropy of $\ensuremath{\Delta}H(\ensuremath{\theta},300)$ and $K$ and $X$ bands shows the expected ${\ensuremath{\omega}}_{0}$ dependence on the Larmor frequency at $\ensuremath{\theta}=54\ifmmode^\circ\else\textdegree\fi{}$.