Search results for "DIPOLE"

Finite Nc corrections in the Balitsky-Kovchegov equation at next-to-leading order

2021

Publisher Copyright: © owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). We study the finite-Nc corrections to the next-to-leading order (NLO) Balitsky-Kovchegov (BK) equation. This contains correlators of six Wilson lines, which we express in terms of the two-point function using the Gaussian approximation. Numerically, the effects of these finite-Nc corrections on the NLO BK equation are found to be smaller than the expected 1/Nc2 ∼ 10%. Corrections may be large for individual correlators, but have less of an influence on the shape of the amplitude as a function of the dipole size. There is a…

Lowest- Q2 measurement of the γp → Δ reaction: Probing the pionic contribution

2006

To determine nonspherical angular momentum amplitudes in hadrons at long ranges (low Q^2), data were taken for the p(\vec{e},e'p)\pi^0 reaction in the Delta region at Q^2=0.060 (GeV/c)^2 utilizing the magnetic spectrometers of the A1 Collaboration at MAMI. The results for the dominant transition magnetic dipole amplitude and the quadrupole to dipole ratios at W=1232 MeV are: M_{1+}^{3/2} = (40.33 +/- 0.63_{stat+syst} +/- 0.61_{model}) (10^{-3}/m_{\pi^+}),Re(E_{1+}^{3/2}/M_{1+}^{3/2}) = (-2.28 +/- 0.29_{stat+syst} +/- 0.20_{model})%, and Re(S_{1+}^{3/2}/M_{1+}^{3/2}) = (-4.81 +/- 0.27_{stat+syst} +/- 0.26_{model})%. These disagree with predictions of constituent quark models but are in reaso…

Effective axial-vector strength and β -decay systematics

2014

We use the weak axial-vector coupling strength as a key parameter to reproduce simultaneously the available data for both the Gamow-Teller and decay rates in nine triplets of isobars with mass numbers . We use the proton-neutron quasiparticle random-phase approximation (pnQRPA) with schematic dipole interaction containing particle-particle and particle-hole parts with mass-dependent strengths. Our analysis points to a strongly quenched effective value , with a relative error of 28%. We then perform a systematic computation of 218 experimentally known and decays with quite a remarkable success. The presently extracted value of should be taken as an effective one, specific for a given nuclear…

Dipole moments of aminophthalimides in the ground and excited electronic states

1995

Quasi-resonant energy transfer in collisions: Na2(A1? u + )+K(4S)

1994

Cross sections for electron energy transfer from the initial rotational stateJ′of the two lowest vibrational levelsv′=0 andv′=1 of excited dimers Na2(A) to potassium atoms as described by Na2(A1Σu+,v′J′)+K(4S)→Na2 (X1Σg+,v″J″)+K(4P)+ΔE have been examined by laser-induced fluorescence. A strong increase of the cross section by as much as an order of magnitude has been observed for those dimerv′J′-levels for which the dipole transitions are close to resonance of the 4S-4P transitions in the atom (ΔE<4 cm−1). The absolute cross sections for energy transfer have been calculated by the Rabitz approximation of first-order perturbation theory. In the case of closest energy resonance (ΔE=0.9 cm−1) …

On the theory of domain switching kinetics in ferroelectrics

2011

Abstract We investigate theoretically the polarization switching kinetics in ferroelectrics, both bulk and thin films samples. In such substances, the domain walls are pinned by (usually dipole) defects, which are present also in ordered samples as technologically unavoidable impurities. This random interaction with dipole pinning centers results, in particular, in exponentially broad distribution of switching times. Under supposition of low pinning centers concentration, we derive the distribution function of switching times showing that it is not simply Lorentzian (as it was first suggested by Tagantsev et al. [Phys. Rev. B 66 (2002) 214109]), but is a “square of Lorentzian”, which is due…

Dipole surface plasmon in large K N + clusters

1993

The dipole surface plasmon forK N + clusters is analyzed using the RPA sum-rule technique within a semiclassical Density Functional Theory and the spherical jellium model. The theoretical frequencies are blue shifted as compared to the experimental ones. The discrepancies between theory and experiment are reduced when considering non-local energy contributions in the density functional and phenomenologically including atomic lattice effects by means of an electron effective mass and a static dielectric constant.

Experimental and theoretical study of thenf-level lifetimes of potassium

2008

The theoretical and experimental values of the 5f ,6 f ,7 f, and 8f radiative lifetimes of neutral potassium are reported. The reduced matrix elements for all allowed electric-dipole nf5/2-nd5/2, nf5/2-nd3/2, and nf7/2-nd5/2 transitions with n =5–8 in K arecalculated using the relativistic linearized coupled-cluster method with single and double excitations of Dirac-Fock wave functions included to all orders in many-body perturbation theory. The resulting electric-dipole matrix elements are used to evaluate the lifetimes of the 5f ,6 f ,7 f, and 8f states in neutral K and their uncertainties. The contributions from the nf5/2-ng7/2, nf7/2-ng7/2, and nf7/2-ng9/2 transitions to the lifetimes o…

Influence of rotational diffusion on the electric field induced effect on the fluorescence spectrum of diluted solutions I. Theory and numerical simu…

1997

Abstract The theory for the calculation of excited state dipole moments from electrooptical emission measurements, developed by Baumann and Deckers (Ber. Bunsenges. Phys. Chem. 81 (1977) 786) presupposes a Boltzmann distribution for the emitting molecules. Using the anisotropic rotational diffusion model and taking into account all important electric field induced effects, we derive equations that describe quantitatively the electric field effect on the fluorescence of an ensemble of solute rigid molecules which are not yet equilibrated with respect to their orientation when emitting. Numerical simulations are performed to compare the general case and the limiting case of a prevailing Boltz…

PNO-CI and CEPA studies of electron correlation effects

1974

Ab initio calculations of the potential curves of low laying electronic states of OH are performed on the basis of a variational configuration interaction wavefunction (PNO-CI) and the coupled electron pair approximation (CEPA). The latter approach yields a ground state potential curve which deviates from the RKR curve by less than 200 cm−1 in the region from 0.7 to 1.6 A. Calculated ground state constants are as follows (experimental values in parentheses): r e = 0.972 (0.971) A, B e = 18.85 (18.87) cm−1, α e = 0.727 (0.714) cm−1, ω e = 3742 (3739) cm−1, ω e χ e = 85.3 (86.4) cm−1, μ0 = 1.686 (1.66) D, D e = 4.35 (4.63) eV,IP = 12.78 (13.36?) eV, El.Aff. = 1.51 (1.83) eV, v 00(2Π↔2Σ+) = 32…