14,546 research outputs found
Optical properties and Raman scattering of vanadium ladder compounds
We investigate electronic and optical properties of the V-based ladder
compounds NaV2O5, the iso-structural CaV2O5, as well as MgV2O5, which differs
from NaV2O5 and CaV2O5 in the c axis stacking. We calculate ab initio the A_g
phonon modes in these compounds as a basis for the investigation of the
electron-phonon and spin-phonon coupling. The phonon modes together with the
dielectric tensors as a function of the corresponding ion displacements are the
starting point for the calculation of the A_g Raman scattering.Comment: 4 pages, 5 figures, .bbl file with references included. Accepted for
publication in Physica Script
Progress in compilation of the 1:2,000,000-scale topographic map
The application of special photogrammetric techniques has enabled the systematic mapping of Mars' topography at a scale of 1:2,000,000, using high-altitude Viking Orbiter pictures. In fiscal 86, compilation was completed of the 24 subquadrangles that make up the quadrangles MC-12, MC-13, MC-14, MC-15, MC-20, and MC-21. This work completes compilation of the 60 topographic maps covering the equatorial belt (lat. + or - 30 deg). The remaining 80 subquadrangles of Mars are planned to be completed within 3 years (27, 27 and 26 subquadrangles, in fiscal 87, 88, and 89, respectively). Elevations on all topographic maps are relative to the Mars topographic datum. The maps have a contour interval of 1 km and a precision of + or - 1 km. The equatorial-belt maps are Mercator projections having true scale at lat. + or - 27.476 deg. These maps provide more precise information than do those previously available and they will help in understanding the geologic processes that have shaped the Martian surface
A compilation system for Venus radar mission (Magellan)
A synthetic aperture radar (SAR) compilation system was developed for extraction of topographic information of Venus from stereoradar imagery to be obtained from the Magellan mission. The system was developed for an AS-11AM analytical stereoplotter. Extensive tests were made on this compilation software by using stereo images from various radar systems, both spaceborne and airborne. Maps were compiled and the precision of planimetry and contour measurement was evaluated. Digital data of some models were also collected for processing orthophoto or perspective views by using the original radar images
Investigation and study of a multi-aperture antenna system final report, 1 jan. - 1 apr. 1964
Multiple aperture adaptive antenna system for telemetry reception from remote space vehicle
Pressure-induced hole doping of the Hg-based cuprate superconductors
We investigate the electronic structure and the hole content in the
copper-oxygen planes of Hg based high Tc cuprates for one to four CuO2 layers
and hydrostatic pressures up to 15 GPa. We find that with the pressure-induced
additional number of holes of the order of 0.05e the density of states at the
Fermi level changes approximately by a factor of 2. At the same time the saddle
point is moved to the Fermi level accompanied by an enhanced k_z dispersion.
This finding explains the pressure behavior of Tc and leads to the conclusion
that the applicability of the van Hove scenario is restricted. By comparison
with experiment, we estimate the coupling constant to be of the order of 1,
ruling out the weak coupling limit.Comment: 4 pages, 4 figure
Optical properties, electron-phonon coupling, and Raman scattering of vanadium ladder compounds
The electronic structure of two V-based ladder compounds, the quarter-filled
NaVO in the symmetric phase and the iso-structural half-filled
CaVO is investigated by ab initio calculations. Based on the
bandstructure we determine the dielectric tensor of these
systems in a wide energy range. The frequencies and eigenvectors of the fully
symmetric A phonon modes and the corresponding electron-phonon and
spin-phonon coupling parameters are also calculated from first-principles. We
determine the Raman scattering intensities of the A phonon modes as a
function of polarization and frequency of the exciting light.
All results, i.e. shape and magnitude of the dielectric function, phonon
frequencies and Raman intensities show very good agreement with available
experimental data.Comment: 11 pages, 10 figure
Experimental recovery of a qubit from partial collapse
We describe and implement a method to restore the state of a single qubit, in
principle perfectly, after it has partially collapsed. The method resembles the
classical Hahn spin-echo, but works on a wider class of relaxation processes,
in which the quantum state partially leaves the computational Hilbert space. It
is not guaranteed to work every time, but successful outcomes are heralded. We
demonstrate using a single trapped ion better performance from this recovery
method than can be obtained employing projection and post-selection alone. The
demonstration features a novel qubit implementation that permits both partial
collapse and coherent manipulations with high fidelity.Comment: 5 pages, 3 figure
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