Search results for "multipole"
showing 10 items of 105 documents
Revisiting the charge density analysis of 2,5-dichloro-1,4-benzoquinone at 20 K
2017
A high-resolution X-ray diffraction measurement of 2,5-dichloro-1,4-benzoquinone (DCBQ) at 20 K was carried out. The experimental charge density was modeled using the Hansen–Coppens multipolar expansion and the topology of the electron density was analyzed in terms of the quantum theory of atoms in molecules (QTAIM). Two different multipole models, predominantly differentiated by the treatment of the chlorine atom, were obtained. The experimental results have been compared to theoretical results in the form of a multipolar refinement against theoretical structure factors and through direct topological analysis of the electron density obtained from the optimized periodic wavefunction. The si…
On the application of an experimental multipolar pseudo-atom library for accurate refinement of small-molecule and protein crystal structures
2007
International audience; With an increasing number of biomacromolecular crystal structures being measured to ultra-high resolution, it has become possible to extend to large systems experimental charge-density methods that are usually applied to small molecules. A library has been built of average multipole populations describing the electron density of chemical groups in all 20 amino acids found in proteins. The library uses the Hansen & Coppens multipolar pseudo-atom model to derive molecular electron density and electrostatic potential distributions. The library values are obtained from several small peptide or amino acid crystal structures refined against ultra-high-resolution X-ray diff…
Spontaneous Scalarization of Charged Black Holes
2018
Extended scalar-tensor-Gauss-Bonnet (eSTGB) gravity has been recently argued to exhibit spontaneous scalarisation of vacuum black holes (BHs). A similar phenomenon can be expected in a larger class of models, which includes e.g. Einstein-Maxwell-scalar (EMS) models, where spontaneous scalarisation of electrovacuum BHs should occur. EMS models have no higher curvature corrections, a technical simplification over eSTGB models that allows us to investigate, fully non-linearly, BH scalarisation in two novel directions. Firstly, numerical simulations in spherical symmetry show, dynamically, that Reissner-Nordstr\"om (RN) BHs evolve into a perturbatively stable scalarised BH. Secondly, we compute…
Searches for small-scale anisotropies from neutrino point sources with three years of IceCube data
2015
Recently, IceCube found evidence for a diffuse signal of astrophysical neutrinos in an energy range of $60\,\mathrm{TeV}$ to the $\mathrm{PeV}$-scale. The origin of those events, being a key to understanding the origin of cosmic rays, is still an unsolved question. So far, analyses have not succeeded to resolve the diffuse signal into point-like sources. Searches including a maximum-likelihood-ratio test, based on the reconstructed directions and energies of the detected down- and up-going neutrino candidates, were also performed on IceCube data leading to the exclusion of bright point sources. In this paper, we present two methods to search for faint neutrino point sources in three years o…
Resonance scattering in macromolecular structure research
2005
Resonance (or anomalous) X-ray scattering of partially ordered macromolecular structures, amorphous materials and solutions is encountered in the near edge region of X-ray absorption edges where the resonant real part f' of atomic form factors shows the strongest dispersion. The requirements of spectral brilliance in the near absorption edges can only be met by synchrotron radiation emitted from high energy electron (positron) storage rings. Resonance scattering yields three basic scattering functions. This compares to contrast variation in neutron scattering. The relations to isomorphous replacement methods of crystallography are discussed. The analysis of the basic scattering functions in…
Electrostatic model and NMR results for EFG tensors in tetragonal BaTiO3
1990
Abstract We present 47,49Ti and 135,137Ba NMR second-order quadrupolar rotation patterns in a tetragonal single domain crystal of BaTiO3. These data will be analysed in terms of a ionic polarizable point multipole model.
Melting and multipole deformation of sodium clusters
1999
Melting and multipole deformations of sodium clusters with up to 55 atoms are studied using an ab initio molecular dynamics method. The melting temperature regions for Na20, Na40, and Na 55 + are estimated. The melting temperature region determined here for Na 55 + agrees with the one determined experimentally. The dominating deformation type observed at the liquid phase for Na20 and Na40 is octupole deformation and for Na14 and Na 55 + quadrupole deformation.
Silence of Binary Kerr Black Holes
2020
A nontrivial S matrix generally implies a production of entanglement: starting with an incoming pure state, the scattering generally returns an outgoing state with nonvanishing entanglement entropy. It is then interesting to ask if there exists a nontrivial S matrix that generates no entanglement. In this Letter, we argue that the answer is the S-matrix for the scattering of classical black holes. We study the spin entanglement in the scattering of arbitrary spinning particles. Augmenting the S-matrix with Thomas–Wigner rotation factors, we derive the entanglement entropy from the gravitational induced 2→2 amplitude. In the Eikonal limit, we find that the relative entanglement entropy, defi…
Recent developments in the evaluation of Mössbauer line intensities
1985
The angular dependence of the intensities of pure or mixed multipole transitions is formulated in a new fashion, which takes into account arbitrary texture of the Mossbauer absorber ranging from complete orientation (single crystals) over preferred orientation to random powders and an anisotropic absorption fraction of the nuclei. The application of the theory is demonstrated by means of typical examples from the literature.
Analysis of the Intermediate-State Contributions to Neutrinoless Double β− Decays
2016
A comprehensive analysis of the structure of the nuclear matrix elements (NMEs) of neutrinoless double beta-minus (0νβ-β-) decays to the0+ground and first excited states is performed in terms of the contributing multipole states in the intermediate nuclei of0νβ-β-transitions. We concentrate on the transitions mediated by the light (l-NMEs) Majorana neutrinos. As nuclear model we use the proton-neutron quasiparticle random-phase approximation (pnQRPA) with a realistic two-nucleon interaction based on the Bonn one-boson-exchangeGmatrix. In the computations we include the appropriate short-range correlations, nucleon form factors, and higher-order nucleonic weak currents and restore the isospi…