130 research outputs found
Relativistic Reduced-Mass and Recoil Corrections to Vacuum Polarization in Muonic Hydrogen, Muonic Deuterium and Muonic Helium Ions
The reduced-mass dependence of relativistic and radiative effects in simple
muonic bound systems is investigated. The spin-dependent nuclear recoil
correction of order (Zalpha)^4 mu^3/m_N^2 is evaluated for muonic hydrogen and
deuterium, and muonic helium ions (mu is the reduced mass and m_N is the
nuclear mass). Relativistic corrections to vacuum polarization of order alpha
(Zalpha)^4 mu are calculated, with a full account of the reduced-mass
dependence. The results shift theoretical predictions. The radiative-recoil
correction to vacuum polarization of order alpha (Z\alpha)^5 ln^2(Zalpha)
mu^2/m_N is obtained in leading logarithmic approximation. The results
emphasize the need for a unified treatment of relativistic corrections to
vacuum polarization in muonic hydrogen, muonic deuterium and muonic helium
ions, where the mass ratio of the orbiting particle to the nuclear mass is
larger than the fine-structure constant.Comment: 6 pages; RevTe
The Lamb shift contribution of very light millicharged particles
The leading order vacuum polarization contribution of very light millicharged
fermions and scalar (spin-0) particles with charge \epsilon e and mass \mu to
the Lamb shift of the hydrogen atom is shown to imply universal, i.e.
\mu-independent, upper bounds on \epsilon: \epsilon \lsim 10^{-4} for \mu \lsim
1 keV in the case of fermions, and for scalars this bound is increased by a
factor of 2. This is in contrast to expectations based on the commonly used
approximation to the Uehling potential relevant only for conventionally large
fermion (and scalar) masses.Comment: 10 pages including 3 figures, version to appear in Physical Review D
(Rapid Communications
Group analysis and renormgroup symmetries
An original regular approach to constructing special type symmetries for
boundary value problems, namely renormgroup symmetries, is presented. Different
methods of calculating these symmetries, based on modern group analysis are
described. Application of the approach to boundary value problems is
demonstrated with the help of a simple mathematical model.Comment: 17 pages, RevTeX LATeX file, to appear in Journal of Mathematical
Physic
Relativistic recoil corrections to the electron-vacuum-polarization contribution in light muonic atoms
The relativistic recoil contributions to the Uehling corrections are
revisited. We consider a controversy in recent calculations based on different
approaches including Breit-type and Grotch-type calculations. We have found
that calculations of those authors were in fact done in different gauges and in
some of those gauges contributions the retardation and two-photon-exchange
effects were missed. We have evaluated such effects and obtained a consistent
result from those approaches. We present a correct expression for the
Grotch-type approach which produces a correct gauge-invariant result. We also
consider a finite-nuclear-size correction for the Uehling term. The results are
presented for muonic hydrogen and deuterium atoms and for muonic helium-3 and
helium-4 ions.Comment: Submitted to Phys. Rev. A; in v.2 results for muonic helium are
correcte
Breit Hamiltonian and QED Effects for Spinless Particles
We describe a simplified derivation for the relativistic corrections of order
for a bound system consisting of two spinless particles. We devote
special attention to pionium, the bound system of two oppositely charged pions.
The leading quantum electrodynamic (QED) correction to the energy levels is of
the order of and due to electronic vacuum polarization. We analyze
further corrections due to the self-energy of the pions, and due to recoil
effects, and we give a complete result for the scalar-QED leading logarithmic
corrections which are due to virtual loops involving only the scalar
constituent particles (the pions); these corrections are of order for S states.Comment: 12 pages, LaTeX; references added (J. Phys. B, in press
Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell during initial stage of shell expansion
Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell, created under laser heating of nanoparticle in water, were theoretically investigated. Vapor shell expansion leads to decreasing up to one to two orders of magnitude in comparison with initial values of scattering and extinction of the radiation with wavelengths 532 and 633 nm by system while shell radius is increased up to value of about two radii of nanoparticle. Subsequent increasing of shell radius more than two radii of nanoparticle leads to rise of scattering and extinction properties of system over initial values. The significant decrease of radiation scattering and extinction by system of nanoparticle-vapor shell can be used for experimental detection of the energy threshold of vapor shell formation and investigation of the first stages of its expansion
Dislocation Kinks in Copper: Widths, Barriers, Effective Masses, and Quantum Tunneling
We calculate the widths, migration barriers, effective masses, and quantum
tunneling rates of kinks and jogs in extended screw dislocations in copper,
using an effective medium theory interatomic potential. The energy barriers and
effective masses for moving a unit jog one lattice constant are close to
typical atomic energies and masses: tunneling will be rare. The energy barriers
and effective masses for the motion of kinks are unexpectedly small due to the
spreading of the kinks over a large number of atoms. The effective masses of
the kinks are so small that quantum fluctuations will be important. We discuss
implications for quantum creep, kink--based tunneling centers, and Kondo
resonances
MoS2@ZnO Nanoheterostructures Prepared by Electrospark Erosion for Photocatalytic Applications
MoS2@ZnO nanoheterostructures were synthesized by electrospark erosion of zinc granules in a hydrogen peroxide solution and simultaneous addition of MoS2 nanostructured powder into the reaction zone. The morphology, size of the crystallites, as well as elemental and phase composition of the prepared structures, were examined using transmission electron microscopy and X-ray diffraction analysis. It was found that the synthesized products represent heterostructures containing MoS2 nanoparticles formed on ZnO nanoparticles. Raman spectroscopy and photoluminescence analysis were also used for characterization of the prepared heterostructures. The obtained MoS2@ZnO nanostructures revealed an intense broad emission band ranging from 425 to 625 nm for samples with different fractions of MoS2. Photocatalytic measurements showed that the maximal hydrogen evolution rate of the prepared nanoheterostructures was about 906.6 μmol·g−1·h−1. The potential of their application in photocatalytic water splitting was also estimated
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