Search results for "Quantum"
showing 10 items of 9714 documents
Nonlinear pressure dependence of the direct band gap in adamantine ordered-vacancy compounds
2010
A strong nonlinear pressure dependence of the optical absorption edge has been measured in defect chalcopyrites CdGa{sub 2}Se{sub 4} and HgGa{sub 2}Se{sub 4}. The behavior is due to the nonlinear pressure dependence of the direct band-gap energy in these compounds as confirmed by ab initio calculations. Our calculations for CdGa{sub 2}Se{sub 4}, HgGa{sub 2}Se{sub 4} and monoclinic {beta}-Ga{sub 2}Se{sub 3} provide evidence that the nonlinear pressure dependence of the direct band-gap energy is a general feature of adamantine ordered-vacancy compounds irrespective of their composition and crystalline structure. The nonlinear behavior is due to a conduction band anticrossing at the {Gamma} po…
The hyperfine structure in the rotational spectra of bromofluoromethane: Lamb-dip technique and quantum-chemical calculations
2008
International audience; The hyperfine structure in the rotational spectra of six isotopic species of bromofluoromethane, namely CH2{79}BrF, CH2{81}BrF, CDH{79}BrF, CDH{81}BrF, CD2{79}BrF, and CD2{81}BrF, has been investigated using the Lamb-dip technique in the submillimeter-wave frequency range. Measurements as well as assignment procedures have been supported by high-level quantum-chemical calculations of the hyperfine parameters at the coupled-cluster level. For all species, the accuracy of the determined rotational and centrifugal distortion constants as well as the bromine quadrupole-coupling constants have been improved with respect to available literature data, whereas the full bromi…
High-pressure structural study of the scheelite tungstatesCaWO4andSrWO4
2005
Angle-dispersive x-ray-diffraction and x-ray-absorption near-edge structure measurements have been performed on ${\mathrm{CaWO}}_{4}$ and ${\mathrm{SrWO}}_{4}$ up to pressures of approximately 20 GPa. Both materials display similar behavior in the range of pressures investigated in our experiments. As in the previously reported case of ${\mathrm{CaWO}}_{4}$, under hydrostatic conditions ${\mathrm{SrWO}}_{4}$ undergoes a pressure-induced scheelite-to-fergusonite transition around 10 GPa. Our experimental results are compared to those found in the literature and are further supported by ab initio total-energy calculations, from which we also predict the instability at larger pressures of the …
Lattice dynamics of wurtzite and rocksalt AlN under high pressure: Effect of compression on the crystal anisotropy of wurtzite-type semiconductors
2008
Raman spectra of aluminum nitride (AlN) under pressure have been measured up to $25\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, i.e., beyond the onset of the wurtzite-to-rocksalt phase transition around $20\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The experimental pressure coefficients for all the Raman-active modes of the wurtzite phase are reported and compared to those obtained from ab initio lattice dynamical calculations, as well as to previous experimental and theoretical results. The pressure coefficients of all the Raman-active modes in wurtzite-type semiconductors (AlN, GaN, InN, ZnO, and BeO), as well as the relatively low bulk modulus and phase transition pressure in wurtzite AlN, a…
Search for Gravitational-wave Signals Associated with Gamma-Ray Bursts during the Second Observing Run of Advanced LIGO and Advanced Virgo
2019
We present the results of targeted searches for gravitational-wave transients associated with gamma-ray bursts during the second observing run of Advanced LIGO and Advanced Virgo, which took place from 2016 November to 2017 August. We have analyzed 98 gamma-ray bursts using an unmodeled search method that searches for generic transient gravitational waves and 42 with a modeled search method that targets compact-binary mergers as progenitors of short gamma-ray bursts. Both methods clearly detect the previously reported binary merger signal GW170817, with p-values of <9.38 10-6 (modeled) and 3.1 10-4 (unmodeled). We do not find any significant evidence for gravitational-wave signals associate…
Theoretical study of the low‐lying states of trans‐1,3‐butadiene
1992
We present extensive ab initio calculations on the low‐lying electronic states of trans‐1,3‐butadiene within the multireference configuration interaction (MRCI) framework by selecting the configurations with a perturbative criterion. The X 1Ag ground state and 1 3Bu, 1 3Ag, 2 1Ag, and 1 1Bu valence excited states have been calculated at a fixed geometry. The results obtained are in good agreement with previous experimental and calculated values, and could help to understand polyene spectroscopy, photochemistry, and photophysics. The advantages of a MRCI method where the most important contributions to the total MRCI wave function, perturbatively selected, are treated variationally, and the …
Potential models for the simulation of methane adsorption on graphene: development and CCSD(T) benchmarks
2018
Different force fields for the graphene–CH4 system are proposed including pseudo-atom and full atomistic models. Furthermore, different charge schemes are tested to evaluate the electrostatic interaction for the CH4 dimer. The interaction parameters are optimized by fitting to interaction energies at the DFT level, which were themselves benchmarked against CCSD(T) calculations. The potentials obtained with both the pseudo-atom and full atomistic approaches describe accurately enough the average interaction in the methane dimer as well as in the graphene–methane system. Moreover, the atom–atom potentials also correctly provide the energies associated with different orientations of the molecu…
Flow cytometry and spectral imaging multiphoton microscopy analysis of CD36 expression with quantum dots 605 of untreated and 7-ketocholesterol-treat…
2006
To evaluate CD36 expression with quantum dots 605 (QDs 605) on untreated and 7-ketocholesterol (7KC)-treated monocytic U937 cells by flow cytometry (FCM) and confocal and multiphoton laser scanning microscopy (CLSM).Cells were analyzed by CLSM, following flow cytometric quantification of CD36 expression and 7KC uptake. Image sequences were obtained by spectral analysis in monophoton and multiphoton CLSM and analyzed by the factor analysis of medical image sequences (FAMIS) algorithm to differentiate emission spectra. In CLSM analysis, cell deposits were screened in ultraviolet excitation modes to optimize the possibilities of QDs 605 and have the benefit of nuclei counterstaining by DAPI.FC…
Transverse-momentum-dependent Multiplicities of Charged Hadrons in Muon-Deuteron Deep Inelastic Scattering
2017
A semi-inclusive measurement of charged hadron multiplicities in deep inelastic muon scattering off an isoscalar target was performed using data collected by the COMPASS Collaboration at CERN. The following kinematic domain is covered by the data: photon virtuality $Q^{2}>1$ (GeV/$c$)$^2$, invariant mass of the hadronic system $W > 5$ GeV/$c^2$, Bjorken scaling variable in the range $0.003 < x < 0.4$, fraction of the virtual photon energy carried by the hadron in the range $0.2 < z < 0.8$, square of the hadron transverse momentum with respect to the virtual photon direction in the range 0.02 (GeV/$c)^2 < P_{\rm{hT}}^{2} < 3$ (GeV/$c$)$^2$. The multiplicities are pres…
Measuring Observable Quantum Contextuality
2016
Contextuality is a central property in comparative analysis of classical, quantum, and supercorrelated systems. We examine and compare two well-motivated approaches to contextuality. One approach (“contextuality-by-default”) is based on the idea that one and the same physical property measured under different conditions (contexts) is represented by different random variables. The other approach is based on the idea that while a physical property is represented by a single random variable irrespective of its context, the joint distributions of the random variables describing the system can involve negative (quasi-)probabilities. We show that in the Leggett-Garg and EPR-Bell systems, the two …