Absorption (logic)

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

Collective excitation interferometry with a toroidal Bose-Einstein condensate

Abstract: The precision of most compact inertial sensing schemes using trapped- and guided-atom interferometers has been limited by uncontrolled phase errors caused by trapping potentials and interactions. Here we propose an acoustic interferometer that uses sound waves in a toroidal Bose-Einstein condensate to measure rotation, and we demonstrate experimentally several key aspects of this type of interferometer. We use spatially patterned light beams to excite counterpropagating sound waves within the condensate and use in situ absorption imaging to characterize their evolution. We present an analysis technique by which we extract separately the oscillation frequencies of the standing-wave acoustic modes, the frequency splitting caused by static imperfections in the trapping potential, and the characteristic precession of the standing-wave pattern due to rotation. Supported by analytic and numerical calculations, we interpret the noise in our measurements, which is dominated by atom shot noise, in terms of rotation noise. While the noise of our acoustic interferometric sensor, at the level of $\ensuremath{\sim}\text{rad}\phantom{\rule{0.16em}{0ex}}{\text{s}}^{\ensuremath{-}1}/\sqrt{\text{Hz}}$, is high owing to rapid acoustic damping and the small radius of the trap, the proof-of-concept device does operate at the high densities and small volumes of trapped Bose-Einstein condensed gases.

The Physical Conditions, Metallicity and Metal Abundance Ratios In a Highly Magnified Galaxy at z = 3.6252

Abstract: We present optical and near-IR imaging and spectroscopy of SGAS J105039.6$+$001730, a strongly lensed galaxy at z $=$ 3.6252 magnified by $>$30$\times$, and derive its physical properties. We measure a stellar mass of log(M$_{*}$/M$_{\odot}$) $=$ 9.5 $\pm$ 0.35, star formation rates from [O II]$\lambda$$\lambda$3727 and H-$\beta$ of 55 $\pm$ 20 and 84 $\pm$ 17 M$_{\odot}$ yr$^{-1}$, respectively, an electron density of n$_{e} \leq$ 10$^{3}$ cm$^{-2}$, an electron temperature of T$_{e} \leq$ 14000 K, and a metallicity of 12+log(O/H) $=$ 8.3 $\pm$ 0.1. The strong C III]$\lambda$$\lambda$1907,1909 emission and abundance ratios of C, N, O and Si are consistent with well-studied starbursts at z $\sim$ 0 with similar metallicities. Strong P Cygni lines and He II$\lambda$1640 emission indicate a significant population of Wolf-Rayet stars, but synthetic spectra of individual populations of young, hot stars do not reproduce the observed integrated P Cygni absorption features. The rest-frame UV spectral features are indicative of a young starburst with high ionization, implying either 1) an ionization parameter significantly higher than suggest by rest-frame optical nebular lines, or 2) differences in one or both of the initial mass function and the properties of ionizing spectra of massive stars. We argue that the observed features are likely the result of a superposition of star forming regions with different physical properties. These results demonstrate the complexity of star formation on scales smaller than individual galaxies, and highlight the importance of systematic effects that result from smearing together the signatures of individual star forming regions within galaxies.

Study of F -Center Formation in KCl on a Picosecond Time Scale

Abstract: We have measured the growth of $F$-band absorption at 532 nm in pure KCl following two-quantum band-gap excitation by a 266-nm pulse. The rise time at $T\ensuremath{\approx}25$ K is 11\ifmmode\pm\else\textpm\fi{}9 psec. Spectral measurements confirm attribution of the early absorption to $F$ centers. This absorption reflects the generation of new Frenkel defects with the $F$ center created directly in its electronic ground state.

Size dependence of L2,3 branching ratio and 2p core-hole screening in x-ray absorption of metal clusters.

Abstract: Resonant $2p$ x-ray absorption spectra of size-selected transition metal ions and clusters consisting of $1\ensuremath{\le}n\ensuremath{\le}200$ atoms are reported. Remnants of atomic multiplet splitting in ${L}_{2,3}$-edge x-ray absorption can be resolved up to the trimer, above which the overall line shape is already bulklike. A strong cluster size dependence of the ${L}_{2,3}$ branching ratio was found for titanium, vanadium, and cobalt clusters. While $3d$ electron delocalization increases with cluster size, the apparent $2p$ spin-orbit splitting remains constant within the error bars. The size dependence of the ${L}_{2,3}$ branching ratio can be attributed to cluster size specific screening of the $2p--3d$ Coulomb interaction by $3d/4s$ valence electrons.

Frequency and temperature dependence of the anomalous ac Hall conductivity in a chiral p x + i p y superconductor with impurities

Abstract: We calculate frequency and temperature dependence of the anomalous ac Hall conductivity induced by impurity scattering in a chiral ${p}_{x}+i{p}_{y}$ superconductor, such as ${\text{Sr}}_{2}{\text{RuO}}_{4}$, with spontaneous time-reversal-symmetry breaking in the absence of an external magnetic field. We consider two models of disorder, Gaussian and non-Gaussian, characterized by the second and third moments of the random impurity potential, respectively. Within both models, we find that the anomalous Hall conductivity has a finite real value at zero frequency, exhibits singularities at the threshold of photon absorption across the superconducting gap, and decays as some power of the high frequency $\ensuremath{\omega}$. The Hall conductivity increases linearly with the decrease in temperature below the superconducting transition and saturates at zero temperature. Using our results for the high-frequency Hall conductivity, we estimate the polar Kerr angle for light reflection from the material and compare it with the experimental measurements in ${\text{Sr}}_{2}{\text{RuO}}_{4}$ by Xia et al., Phys. Rev. Lett. 97, 167002 (2006).