219 research outputs found
Comparative study of the electron- and positron-atom bremsstrahlung
Fully relativistic treatment of the electron-atom and positron-atom
bremsstrahlung is reported. The calculation is based on the partial-wave
expansion of the Dirac scattering states in an external atomic field. A
comparison of the electron and positron bremsstrahlung is presented for the
single and double differential cross sections and the Stokes parameters of the
emitted photon. It is demonstrated that the electron-positron symmetry of the
bremsstrahlung spectra, which is nearly exact in the nonrelativistic regime, is
to a large extent removed by the relativistic effects
Parity nonconservation effect in the resonance elastic electron scattering on heavy He-like ions
We investigate the parity nonconservation effect in the elastic scattering of
polarized electrons on heavy He-like ions, being initially in the ground state.
The enhancement of the parity violation is achieved by tuning the energy of the
incident electron in resonance with quasidegenerate doubly-excited states of
the corresponding Li-like ion. We consider two possible scenarios. In the first
one we assume that the polarization of the scattered electron is measured,
while in the second one it is not detected.Comment: 13 pages, 3 figures, 2 table
Parity nonconservation effect in the dielectronic recombination of polarized electrons with heavy He-like ions
We investigate the parity nonconservation (PNC) effect in the dielectronic
recombination (DR) of a polarized electron with a heavy He-like ion into
doubly-excited and states of Li-like ion. We determine the
nuclear charge number for which these opposite-parity levels are near to
cross and, therefore, the PNC effect will be significantly enhanced.
Calculations are performed for quantum numbers and .Comment: 12 pages, 1 figur
Polarization correlations in the two--photon decay of hydrogen--like ions
Polarization properties of the photons emitted in the two-photon decay of
hydrogen-like ions are studied within the framework of the density matrix and
second-order perturbation theory. In particular, we derive the polarization
correlation function that gives the probability of the (two-photon) coincidence
measurement performed by polarization-sensitive detectors. Detailed
calculations of this function are performed for the
transition in neutral hydrogen as well as Xe and U ions. The
obtained results allow us to understand the influence of relativistic and
non-dipole effects on the polarization correlations in the bound-bound
two-photon transitions in heavy ions
Parity violation in the resonance elastic electron scattering on He-like uranium
Synopsis Parity violation on the cross section of the resonance elastic electron scattering by He-like uranium ion is studied. It is assumed that the incident electron is polarized and tuned in resonance with one of the close-lying opposite-parity states
Relativistic polarization analysis of Rayleigh scattering by atomic hydrogen
A relativistic analysis of the polarization properties of light elastically
scattered by atomic hydrogen is performed, based on the Dirac equation and
second order perturbation theory. The relativistic atomic states used for the
calculations are obtained by making use of the finite basis set method and
expressed in terms of splines and polynomials. We introduce two
experimental scenarios in which the light is circularly and linearly polarized,
respectively. For each of these scenarios, the polarization-dependent angular
distribution and the degrees of circular and linear polarization of the
scattered light are investigated as a function of scattering angle and photon
energy. Analytical expressions are derived for the polarization-dependent
angular distribution which can be used for scattering by both hydrogenic as
well as many-electron systems. Detailed computations are performed for Rayleigh
scattering by atomic hydrogen within the incident photon energy range 0.5 to 10
keV. Particular attention is paid to the effects that arise from higher
(nondipole) terms in the expansion of the electron-photon interaction.Comment: 8 pages, 5 figure
A 2D position sensitive germanium detector for spectroscopy and polarimetry of high-energetic x-rays
We report on a first prototype 2D ÎĽ-strip germanium detector, developed at IKP-JĂĽlich, and its performance test at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Beside an accurate determination of the detector response function, the polarization sensitivity has been addressed in this study. For this purpose photon beams at energies of 60 keV and 210 keV have been used
Core-coupled states and split proton-neutron quasi-particle multiplets in 122-126Ag
Neutron-rich silver isotopes were populated in the fragmentation of a 136Xe
beam and the relativistic fission of 238U. The fragments were mass analyzed
with the GSI Fragment separator and subsequently implanted into a passive
stopper. Isomeric transitions were detected by 105 HPGe detectors. Eight
isomeric states were observed in 122-126Ag nuclei. The level schemes of
122,123,125Ag were revised and extended with isomeric transitions being
observed for the first time. The excited states in the odd-mass silver isotopes
are interpreted as core-coupled states. The isomeric states in the even-mass
silver isotopes are discussed in the framework of the proton-neutron split
multiplets. The results of shell-model calculations, performed for the most
neutron-rich silver nuclei are compared to the experimental data
Exclusive electroproduction of K+ Lambda and K+ Sigma^0 final states at Q^2 = 0.030-0.055 (GeV/c)^2
Cross section measurements of the exclusive p(e,e'K+)Lambda,Sigma^0
electroproduction reactions have been performed at the Mainz Microtron MAMI in
the A1 spectrometer facility using for the first time the Kaos spectrometer for
kaon detection. These processes were studied in a kinematical region not
covered by any previous experiment. The nucleon was probed in its third
resonance region with virtual photons of low four-momenta, Q^2= 0.030-0.055
(GeV/c)^2. The MAMI data indicate a smooth transition in Q^2 from
photoproduction to electroproduction cross sections. Comparison with
predictions of effective Lagrangian models based on the isobar approach reveal
that strong longitudinal couplings of the virtual photon to the N* resonances
can be excluded from these models.Comment: 16 pages, 7 figure
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