Absorption (logic)

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

Influence of H-D isotopic substitution on the protonic conductivity of LiNbO3.

Abstract: The electric dc dark conductivity in congruent ${\mathrm{LiNbO}}_{3}$ has been studied in the temperature range 80--600 \ifmmode^\circ\else\textdegree\fi{}C as a function of the proton and deuteron concentration and the driving electric field. The conductivity was found to follow an Arrhenius-like behavior with an activation energy equal for protons and deuterons, ${\mathrm{\ensuremath{\varepsilon}}}_{\mathrm{act}}$=1.23 eV. The pre-exponential factor ${\mathrm{\ensuremath{\sigma}}}_{0}$ shows a linear concentration dependence for both H and D, but with different slopes. The ratio of the slopes yields (\ensuremath{\partial}${\mathrm{\ensuremath{\sigma}}}_{0}$/\ensuremath{\partial}c${)}_{\mathrm{H}}$/(\ensuremath{\partial}${\mathrm{\ensuremath{\sigma}}}_{0}$/\ensuremath{\partial}c${)}_{\mathrm{D}}$=1.36. This agrees with the mass dependence of the attempt frequencies in a hopping model of protons and deuterons and rules out models of OH-OD migration. The conductivity was found to be independent of the electric field up to values of ${10}^{5}$ V/cm, which is comparable to inner electric fields in volume holograms in ${\mathrm{LiNbO}}_{3}$. In the temperature range accessible to both methods, the dc and the holographically measured values of the conductivity agree very well, displaying the same temperature and concentration dependence. The charge-carrier concentration was determined from the integrated absorption strength of the ir OH-OD stretch-mode absorption of proton- and deuteron-exchanged waveguides with a known rate of exchange of Li by H-D, yielding an oscillator strength ${\mathit{f}}_{\mathrm{H}}$=1.7\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}2}$.

Interband Impact Ionization and Nonlinear Absorption of Terahertz Radiation in Semiconductor Heterostructures

Abstract: We have theoretically investigated nonlinear free-carrier absorption of terahertz (THz) radiation in $\mathrm{I}\mathrm{n}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}\mathrm{S}\mathrm{b}$ heterojunctions. By considering multiple photon process and conduction-valence interband impact ionization (II), we have determined the field and frequency dependent absorption rate. It is shown that (i) electron-disorder scatterings are important at low to intermediate field, and (ii) most importantly, the high field absorption is dominated by II processes. Our theory can satisfactorily explain a long-standing experimental result on the nonlinear absorption in the THz regime.

Paramagnetic Resonance and Optical Absorption Spectra of Cr 3+ in MgO

Abstract: The paramagnetic resonance spectrum of the trivalent chromium ion has been detected at a wavelength of 1.2 cm. The spectrum is isotropic with one line at $g=1.9800\ifmmode\pm\else\textpm\fi{}0.0006$. The hyperfine structure of the ${\mathrm{Cr}}^{53}$ isotope in its natural abundance was detected. The hyperfine structure constant $A=(1.60\ifmmode\pm\else\textpm\fi{}0.03)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$ permits an evaluation of the nuclear magnetic moment as 0.475 nm. The narrow line and the failure to observe any ground state splitting show that the trivalent chromium ion is exposed to a very pure cubic field. There is no indication of associated vacancies with the ${\mathrm{Cr}}^{3+}$ ion. Optical absorption lines were found at 16 000, 22 700, and 29 700 ${\mathrm{cm}}^{\ensuremath{-}1}$ as well as a beginning of absorption at 46 000 ${\mathrm{cm}}^{\ensuremath{-}1}$. The 16 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ line is caused either by a quartet-doublet transition or by the ${\mathrm{Cr}}^{2+}$ ion. The other absorption lines can be fitted with $Dq=2270$ ${\mathrm{cm}}^{\ensuremath{-}1}$ and the $^{4}P$ state at 10 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ above the $^{4}F$ state. An analysis of the paramagnetic and optical absorption spectra indicate very strong crystal field and some covalent bonding. Probably the ${\mathrm{Cr}}^{3+}$ and the surrounding six oxygen atoms have to be regarded as a very tightly knit unit.

Standard neutrino spectrum from B 8 decay

Abstract: We present a systematic evaluation of the shape of the neutrino energy spectrum produced by beta decay of $^{8}\mathrm{B}$. We place special emphasis on determining the range of uncertainties permitted by existing laboratory data and theoretical ingredients (such as forbidden and radiative corrections). We review and compare the available experimental data on the $^{8}\mathrm{B}$(${\mathrm{\ensuremath{\beta}}}^{+}$${)}^{8}$Be(2\ensuremath{\alpha}) decay chain. We analyze the theoretical and experimental uncertainties quantitatively. We give a numerical representation of the best-fit (standard-model) neutrino spectrum, as well as two extreme deviations from the standard spectrum that represent the total (experimental and theoretical) effective \ifmmode\pm\else\textpm\fi{}3\ensuremath{\sigma} deviations. Solar neutrino experiments that are currently being developed will be able to measure the shape of the $^{8}\mathrm{B}$ neutrino spectrum above about 5 MeV. An observed distortion of the $^{8}\mathrm{B}$ solar neutrino spectrum outside the range given in the present work could be considered as evidence, at an effective significance level greater than three standard deviations, for physics beyond the standard electroweak model. We use the most recent available experimental data on the Gamow-Teller strengths in the A=37 system to calculate the $^{8}\mathrm{B}$ neutrino absorption cross section on chlorine: ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{Cl}}$=(1.14\ifmmode\pm\else\textpm\fi{}0.11)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}42}$ ${\mathrm{cm}}^{2}$ (\ifmmode\pm\else\textpm\fi{}3\ensuremath{\sigma} errors). The chlorine cross section is also given as a function of the neutrino energy. The $^{8}\mathrm{B}$ neutrino absorption cross section in gallium is ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{Ga}}$=(2.${46}_{\mathrm{\ensuremath{-}}1.1}^{+2.1}$)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}42}$ ${\mathrm{cm}}^{2}$ (\ifmmode\pm\else\textpm\fi{}3\ensuremath{\sigma} errors). \textcopyright{} 1996 The American Physical Society.

Carrier confinement and special crystallite dimensions in layered semiconductor colloids.

Abstract: Microcrystallites of the layered semiconductor ${\mathrm{PbI}}_{2}$ were prepared in colloidal form and examined by transmission electron microscopy and optical absorption. The crystallites have lateral dimensions grouped around 12, 18, and 29 A\r{} corresponding to close-packed clusters with bulk ${\mathrm{PbI}}_{2}$ symmetry. Blue-shifted absorption features can be explained by carrier confinement in these differently sized crystallites, each a single layer (\ensuremath{\sim}7 A\r{}) thick.