Search results for "Elastic"

Radiative kaon capture on nuclei.

1990

Hypernuclear formation through the radiative capture of in-flight ${\mathit{K}}^{\mathrm{\ensuremath{-}}}$ is studied in a distorted wave impluse approximation approach. The elementary operator is obtained from first-order Feynman diagrams and is constrained by the reactions ${\mathit{K}}^{\mathrm{\ensuremath{-}}}$p\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma} and, via crossing, by \ensuremath{\gamma}p\ensuremath{\rightarrow}${\mathit{K}}^{+}$\ensuremath{\Lambda}. The ${\mathit{K}}^{\mathrm{\ensuremath{-}}}$ distortion has been included via a simple optical potential which is in agreement with ${\mathit{K}}^{\mathrm{\ensuremath{-}}}$ elastic scattering on nuclei. Using the…

Parity-violating asymmetry in elastic electron-nucleus scattering due to weak neutral currents

1980

Parity-violating asymmetries are calculated for elastic scattering of electrons on nuclei of arbitrary spin and isospin. Possible dependences on nuclear-model input are shown to be weak. Elastic electron scattering at intermediate energies may become an important tool in studying the structure of hadronic weak neutral currents.

Elastic light scattering from semiconductor structures: Localized versus propagating intermediate electronic excitations

1995

We present a theoretical study of the relative role of localized and propagating intermediate electronic states in the processes of elastic scattering of light. Only localized excitations lead to isotropic scattering in lowest-order perturbation theory. Inhomogeneous broadening of the optical transition affects the scattering efficiency from the ordered and disordered array of localized states in a qualitatively different way. The propagating electronic excitations may only contribute to elastic light scattering via higher-order processes. The scattering of excitons by impurities or the interface roughness potential is suggested as a mechanism for the contribution of propagating excitations…

Transfer reactions on light exotic nuclei studied with CHIMERA detector at LNS

2014

The kinematical coincidence method is used to extract angular distribution of elastic scattering and transfer reactions. The detected light particle energy spectra are used to extract the angular distribution with around 1° resolution in the Center of Mass (CM) system. Examples with 10Be beam are presented. In the case of proton scattering, γ-ray coincidences are used to discriminate excited levels population from elastic scattering. © Owned by the authors, published by EDP Sciences, 2014.

The Few-Body Coulombian Problem

1999

Recent advances in the treatment of scattering of charged composite particles are reviewed. In a first part I report on developments of the theory. Specifically I describe the recent completion of the derivation of the co-ordinate space asymptotic behaviour of the wave function for three charged particles in the continuum. This knowledge is increasingly being made use of in attempts to ‘derive’ three-Coulomb particle wave functions to be used in all of configuration space which are solutions of the Schrodinger equation, though not everywhere but at least in one or preferably all of the asymptotic regions. Their practical application in approximate calculations of ionisation and breakup proc…

Spin-coupling topology in the copper hexamer compounds A2Cu3O(SO4)3 (A=Na, K)

2020

The compounds ${A}_{2}\mathrm{C}{\mathrm{u}}_{3}\mathrm{O}{(\mathrm{S}{\mathrm{O}}_{4})}_{3}$ $(A=\mathrm{Na},\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ are characterized by copper hexamers that are weakly coupled to realize antiferromagnetic order below ${T}_{N}\ensuremath{\approx}3\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. They constitute quantum spin systems with $S=1$ triplet ground states. We investigated the energy-level splittings of the copper hexamers by inelastic neutron scattering experiments covering the entire range of the magnetic excitation spectra. The observed transitions are governed by very unusual selection rules that we ascribe to the underlying spin-coupling topology. This…

Theory of vibrational anomalies in glasses

2015

Abstract The theory of elasticity with spatially fluctuating elastic constants (heterogeneous-elasticity theory) is reviewed. It is shown that the vibrational anomalies associated with the boson peak can be qualitatively and quantitatively explained in terms of this theory. Two versions of a mean-field theory for solving the stochastic equation of motion are presented: the coherent-potential approximation (CPA) and the self-consistent Born approximation (SCBA). It is shown that the latter is included in the former in the Gaussian and weak-disorder limit. We are able to discuss and explain cases in which the change of the vibrational spectrum by varying an external parameter can be accounted…

Can mechanical energy vanish into thin air?

2018

An energy residual-based approach to gradient effects within the mechanics of generalized continua

2012

AbstractGeneralized continua exhibiting gradient effects are addressed through a method grounded on the energy residual (ER)-based gradient theory by the first author and coworkers. A main tool of this theory is the Clausius-Duhem inequality cast in a form differing from the classical one only by a nonstandard extra term, the (nonlocality) ER, required to satisfy the insulation condition (its global value has to vanish or to take a known value). The ER carries in the nonlocality features of the mechanical problem through a strain-like rate field, being the specific nonlocality source, and a concomitant higher-order long-range stress (or microstress) field. The thermodynamic restrictions on …

Modulating the magnetosphere of magnetars by internal magneto-elastic oscillations

2014

We couple internal torsional, magneto-elastic oscillations of highly magnetized neutron stars (magnetars) to their magnetospheres. The corresponding axisymmetric perturbations of the external magnetic field configuration evolve as a sequence of linear, force-free equilibria that are completely determined by the background magnetic field configuration and by the perturbations of the magnetic field at the surface. The perturbations are obtained from simulations of magneto-elastic oscillations in the interior of the magnetar. While such oscillations can excite travelling Alfv\'en waves in the exterior of the star only in a very limited region close to the poles, they still modulate the near ma…