Search results for " Polarization"
showing 10 items of 668 documents
Minkowskian description of polarized light and polarizers.
2002
A conventional Stokes description of polarized light is considered in a four-dimensional Lorentzian space, developing a seminal idea of Paul Soleillet [Ann. Phys. (Paris) 12, 23 (1929)]. This provides a striking interpretation for the degree of polarization and the Stokes decomposition of light beams. Malus law and reciprocity theorems for polarizers are studied using this Lorentzian formalism.
Circular Polarization of External Bremsstrahlung Produced by Beta Rays
1958
For energies smaller than 600 kev, the polarization was previously measured using forward scattering from magnetized iron, but a quantitative comparison was not performed. Computations were done for monoenergetic electrons falling on a thin absorber, whereas in all experiments the whole beta spectruan and thick absorbers were used. It is shown thnt even in this case a comparison with theory is possible as the diffusion of the electrons in the absorber has practically no influence on the polarization. Strong dependence of the circular polarization on the atomic number of the absorber is investigated. (W.D.M.)
Polarization and angular distribution of the radiation emitted in laser-assisted recombination
2007
The effect of an intense external linear polarized radiation field on the angular distributions and polarization states of the photons emitted during the radiative recombination is investigated. It is predicted, on symmetry grounds, and corroborated by numerical calculations of approximate recombination rates, that emission of elliptically polarized photons occurs when the momentum of the electron beam is not aligned to the direction of the oscillating field. Moreover, strong modifications to the angular distributions of the emitted photons are induced by the external radiation field.
Formation of Wigner molecules in small quantum dots
2000
It was recently argued that in small quantum dots the electrons could crystallize at much higher densities than in the infinite two-dimensional electron gas. We compare predictions that the onset of spin polarization and the formation of Wigner molecules occurs at a density parameter $r_s\approx 4 a_B^*$ to the results of a straight-forward diagonalization of the Hamiltonian matrix.
Correlation and spin polarization in quantum dots: Local spin density functional theory revisited
2005
Using quantum dot artificial atoms as a simple toy model, we reflect on the question of whether spin density functional theory (SDFT) can accurately describe correlation effects in low-dimensional fermion systems. Different expressions for the local density approximation of the exchange-correlation energy for the two-dimensional electron gas, such as the much-used functional of Tanatar and Ceperley, and the recent suggestion by Attaccalite et al., are compared with the results of a numerical diagonalization of the many-body Hamiltonian matrix in the limit of small electron numbers. For systems with degeneracies, as shown in the present work for the example of a spin triplet with S = 1, the …
Nonlinear magneto-optical resonances for systems withJ∼100observed in K2molecules
2012
We present the results of an experimental as well as a theoretical study of nonlinear magneto-optical resonances in diatomic potassium molecules in the electronic ground state with large values of the angular momentum quantum number $J\ensuremath{\sim}100$. At zero magnetic field, the absorption transitions are suppressed because of population trapping in the ground state due to Zeeman coherences between magnetic sublevels of this state along with depopulation pumping. The destruction of such coherences in an external magnetic field was used to study the resonances in this work. K${}_{2}$ molecules were formed in a glass cell filled with potassium metal at a temperature above 150 ${}^{\ensu…
Global fits of the SM parameters
2019
I present a global survey of weak mixing angle measurements and other precision experiments and discuss the issue of correlations of the theoretical uncertainties in precision observables. Hadronic vacuum polarization effects complicate global fits in various ways and are also covered alongside some representative fit results.
Static quantum corrections to the Schwarzschild spacetime
2005
We study static quantum corrections of the Schwarzschild metric in the Boulware vacuum state. Due to the absence of a complete analytic expression for the full semiclassical Einstein equations we approach the problem by considering the s-wave approximation and solve numerically the associated backreaction equations. The solution, including quantum effects due to pure vacuum polarization, is similar to the classical Schwarzschild solution up to the vicinity of the classical horizon. However, the radial function has a minimum at a time-like surface close to the location of the classical event horizon. There the g_{00} component of the metric reaches a very small but non-zero value. The analys…
Compton transmission polarimeter for a very precise polarization measurement within a wide range of electron currents
2011
For new experiments with polarized electron and positron beams the precise and quick measurement of the beam polarization is required. The relative electron polarization has been monitored on-line using a compact transmission Compton polarimeter for a wide range of average electron currents up to 100/μA and electron beam energy of 3.5 MeV. The asymmetry induced by the beam polarization can be monitored precisely with ΔA/A < 0.2 %. Even small relative variations of the beam polarization during a beam time may be detected using this polarimeter, such as an increase ~ 1 % and subsequent decrease of the beam polarization.
Anomalous properties of hot dense nonequilibrium plasmas
2005
A concise overview of a number of anomalous properties of hot dense nonequilibrium plasmas is given. The possibility of quasistationary megagauss magnetic field generation due to Weibel instability is discussed for plasmas created in atom tunnel ionization. The collisionless absorption and reflection of a test electromagnetic wave normally impinging on the plasma with two-temperature bi-maxwellian electron velocity distribution function are studied. Due to the wave magnetic field influence on the electron kinetics in the skin layer the wave absorption and reflection significantly depend on the degree of the electron temperature anisotropy. The linearly polarized impinging wave during reflec…