151 research outputs found
Quantum mechanical evolution operator in the presence of a scalar linear potential: discussion on the evolved state
We discuss the form of the wave-function of a state subjected to a scalar
linear potential, paying special attention to quantum tunneling. We analyze the
phases acquired by the evolved state and show that some of them have a pure
quantum mechanical origin. In order to measure one of these phases, we propose
a simple experimental scenario. We finally apply the evolution equations to
re-analyze the Stern\&Gerlach experiment and to show how to manipulate spin by
employing constant electric fields.Comment: in press in Physica Script
Angular and polarization analysis for two-photon decay of 2s hyperfine states of hydrogenlike Uranium
The amplitude of two-photon transitions between hyperfine states in
hydrogenlike ions is derived based on relativistic Dirac equation and second
order perturbation theory. We study angular and linear polarization properties
of the photon pair emitted in the decay of states, where spin-flip and
non-spin-flip transitions are highlighted. We pay particular attention to
hydrogenlike uranium, since it is an ideal candidate for investigating
relativistic and high-multipole effects, such as spin-flip transitions. Two
types of emission patterns are identified: i) non-spin-flip transitions are
found to be characterized by an angular distribution of the type
while the polarizations of the emitted photons
are parallel; ii) spin-flip transitions have somewhat smaller decay rates and
are found to be characterized by an angular distribution of the type
while the polarizations of the emitted photons
are orthogonal, where is the angle between photons directions.
Deviations due to non-dipole and relativistic contributions are evaluated for
both types of transitions. This work is the first step toward exploring the
effect of nucleus over the the angular and polarization properties of the
photon pairs emitted by two-photon transitions.Comment: 6 pages, 3 figures,will be published in Phys. Rev. A (2014). arXiv
admin note: substantial text overlap with arXiv:1203.660
Spin effects probed by Rayleigh X-ray scattering off hydrogenic ions
We study the polarization characteristics of x-ray photons scattered by
hydrogenic atoms, based on the Dirac equation and second-order perturbation
theory. The relativistic states used in calculations are obtained using the
finite basis set method and expressed in terms of B-splines and B-polynomials.
We derive general analytical expressions for the polarization-dependent total
cross sections, which are applicable to any atom and ion, and evaluate them
separately for linear and circular polarization of photons. In particular,
detailed calculations are performed for the integrated Stokes parameters of the
scattered light for hydrogen as well as hydrogenlike neon and argon. Analyzing
such integrated Stokes parameters, special attention is given to the
electron-photon spin-spin interaction, which mostly stems from the
magnetic-dipole contribution of the electron-photon interaction. Subsequently,
we find an energy window for the selected targets in which such spin-spin
interactions can be probed.Comment: 8 pages,ures 4 fig, To be appeared in Radiat. Phys. Chem. arXiv admin
note: text overlap with arXiv:1208.308
Photon-photon polarization correlations as a tool for studying parity non-conservation in heliumlike Uranium
Due to electron-nucleus weak interaction, atomic bound states with different
parities turn out to be mixed. We discuss a prospect for measuring the mixing
parameter between the nearly degenerate metastable states 1s_{1/2} 2s_{1/2} : J
= 0 and 1s_{1/2} 2p_{1/2} : J = 0 in heliumlike Uranium. Our analysis is based
on the polarization properties of the photons emitted in the two-photon decays
of such states.Comment: 3 figure
Polarization and correlation phenomena in the two-photon absorption and decay of heavy ions
In dieser Arbeit untersuchen wir Zwei-Photonenbergänge zwischen gebunden Zuständen in Atomen und Ionen. Nach einer Einfhrung in die relativistische Diracgleichung und Störungstheorie erster und zweiter Ordnung, analysieren wir die spektrale Verteilung sowie die Winkel- und Polarisationseigenschaften der emittierten Photonen. Die Arbeit beinhaltet eine Untersuchung der Quantenkorrelation (Verschränkung), die der Polarisationszustand der Photonen besitzt, wie auch mögliche Anwendungen der Zwei-Photonenübergänge im Hinblick auf Studien zur Paritätsverletzung
Leptospira Infections in Domestic and Wild Animals
Leptospirosis is a worldwide-distributed, re-emerging zoonosis due to the large variety of wild and domestic animal species that can play the role of natural or accidental host. Currently, specific animal species play an important role as the reservoir for particular Leptospira serovars, although recent investigations have highlighted new host-pathogen interactions involved in Leptospira epidemiology. Furthermore, the constant modification of ecosystems and wildlife habitats and the constantly increasing number of animal species moving towards urban or peri-urban areas are increasing the possibility of direct or indirect contacts between wildlife and domestic animals; furthermore, the constant modification of animal leptospirosis also causes problems for human health. The studies published in this Special Issue have evidenced and confirmed the hidden role of a large variety of animal species, domestic and wild, in the leptospirosis epidemiology. They highlighted the necessity for continuous monitoring and large-scale surveillance studies to better understand this neglected and re-emerging zoonosis
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
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