277 research outputs found
Lamb shift in muonic helium ion
The Lamb shift (2P_{1/2}-2S_{1/2}) in the muonic helium ion (mu ^4_2He)^+ is
calculated with the account of contributions of orders alpha^3, alpha^4,
alpha^5 and alpha^6. Special attention is given to corrections of the electron
vacuum polarization, the nuclear structure and recoil effects. The obtained
numerical value of the Lamb shift 1379.028 meV can be considered as a reliable
estimate for the comparison with experimental data.Comment: 18 pages, 11 figure
A cluster-separable Born approximation for the 3D reduction of the three-fermion Bethe-Salpeter equation
We perform a 3D reduction of the two-fermion Bethe-Salpeter equation based on
Sazdjian's explicitly covariant propagator, combined with a covariant
substitute of the projector on the positive-energy free states. We use this
combination in the two fermions in an external potential and in the
three-fermion problems. The covariance of the two-fermion propagators insures
the covariance of the two-body equations obtained by switching off the external
potential, or by switching off all interactions between any pair of two
fermions and the third one, even if the series giving the 3D potential is
limited to the Born term or more generally truncated. The covariant substitute
of the positive energy projector preserves the equations against continuum
dissolution without breaking the covariance.Comment: 21 pages, 1 figure This article has been deeply modified after
refereeing. The presentation has been improved and examples have been added.
Three subsections have been added (transition matrix elements, two-body
limits, covariant Salpeter's equation). submitted to Journal of Physics
Stark shift and parity non-conservation for near-degenerate states of xenon
We identify a pair of near-degenerate states of opposite parity in atomic Xe,
the 5p^5 10s \,\, ^2[3/2]_2^o at cm and 5p^5 6f
\,\, ^2[5/2]_2 at cm, for which parity- and
time-odd effects are expected to be enhanced by the small energy separation. We
present theoretical calculations which indicate narrow widths for both states
and we report a calculated value for the weak matrix element, arising from
configuration mixing, of Hz for Xe. In addition, we measured
the Stark effect of the and
() states. The Stark-shift of the states
is observed to be negative, revealing the presence of nearby states at
higher energies, which have not been observed before. The Stark-shift
measurements imply an upper limit on the weak matrix element of Hz
for the near-degenerate states (10s \,\, ^2[3/2]_2^o and 6f \,\,
^2[5/2]_2), which is in agreement with the presented calculations.Comment: 11 pages, 6 figure
Accurate spline solutions of the Dirac equation with parity-nonconserving potential
The complete system of the B-spline solutions for the Dirac equation with the
parity-nonconserving (PNC) weak interaction effective potential is obtained.
This system can be used for the accurate evaluation of the radiative
corrections to the PNC amplitudes in the multicharged ions and neutral atoms.
The use of the scaling procedure allows for the evaluation of the PNC matrix
elements with relative accuracy .Comment: 7 page
Correlated many-body treatment of Breit interaction with application to cesium atomic properties and parity violation
Corrections from Breit interaction to basic properties of atomic 133Cs are
determined in the framework of third-order relativistic many-body perturbation
theory. The corrections to energies, hyperfine-structure constants,
off-diagonal hyperfine 6S-7S amplitude, and electric-dipole matrix elements are
tabulated. It is demonstrated that the Breit corrections to correlations are
comparable to the Breit corrections at the Dirac-Hartree-Fock level.
Modification of the parity-nonconserving (PNC) 6S-7S amplitude due to Breit
interaction is also evaluated; the resulting weak charge of Cs shows no
significant deviation from the prediction of the standard model of elementary
particles. The neutron skin correction to the PNC amplitude is also estimated
to be -0.2% with an error bound of 30% based on the analysis of recent
experiments with antiprotonic atoms. The present work supplements publication
[A. Derevianko, Phys. Rev. Lett. 85, 1618 (2000)] with a discussion of the
formalism and provides additional numerical results and updated discussion of
parity violation.Comment: 16 pages; 5 figs; submitted to Phys. Rev.
Two-Loop Polarization Contributions to Radiative-Recoil Corrections to Hyperfine Splitting in Muonium
We calculate radiative-recoil corrections of order
to hyperfine splitting in muonium generated by the
diagrams with electron and muon polarization loops. These corrections are
enhanced by the large logarithm of the electron-muon mass ratio. The leading
logarithm cubed and logarithm squared contributions were obtained a long time
ago. The single-logarithmic and nonlogarithmic contributions calculated here
improve the theory of hyperfine splitting, and affect the value of the
electron-muon mass ratio extracted from the experimental data on the muonium
hyperfine splitting.Comment: 15 pages, 11 figure
Theory of muonic hydrogen - muonic deuterium isotope shift
We calculate the corrections of orders alpha^3, alpha^4 and alpha^5 to the
Lamb shift of the 1S and 2S energy levels of muonic hydrogen (mu p) and muonic
deuterium (mu d). The nuclear structure effects are taken into account in terms
of the proton r_p and deuteron r_d charge radii for the one-photon interaction
and by means of the proton and deuteron electromagnetic form factors in the
case of one-loop amplitudes. The obtained numerical value of the isotope shift
(mu d) - (mu p) for the splitting (1S-2S) 101003.3495 meV can be considered as
a reliable estimation for corresponding experiment with the accuracy 10^{-6}.
The fine structure interval E(1S)-8E(2S) in muonic hydrogen and muonic
deuterium are calculated.Comment: 22 pages, 7 figure
Nuclear Sizes and the Isotope Shift
Darwin-Foldy nuclear-size corrections in electronic atoms and nuclear radii
are discussed from the nuclear-physics perspective. Interpretation of precise
isotope-shift measurements is formalism dependent, and care must be exercised
in interpreting these results and those obtained from relativistic electron
scattering from nuclei. We strongly advocate that the entire nuclear-charge
operator be used in calculating nuclear-size corrections in atoms, rather than
relegating portions of it to the non-radiative recoil corrections. A
preliminary examination of the intrinsic deuteron radius obtained from
isotope-shift measurements suggests the presence of small meson-exchange
currents (exotic binding contributions of relativistic order) in the nuclear
charge operator, which contribute approximately 1/2%.Comment: 17 pages, latex, 1 figure -- Submitted to Phys. Rev. A -- epsfig.sty
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Extension of the sum rule for the transition rates between multiplets to the multiphoton case
The sum rule for the transition rates between the components of two
multiplets, known for the one-photon transitions, is extended to the
multiphoton transitions in hydrogen and hydrogen-like ions. As an example the
transitions 3p-2p, 4p-3p and 4d-3d are considered. The numerical results are
compared with previous calculations.Comment: 10 pages, 4 table
Calculation of the Electron Self Energy for Low Nuclear Charge
We present a nonperturbative numerical evaluation of the one-photon electron
self energy for hydrogenlike ions with low nuclear charge numbers Z=1 to 5. Our
calculation for the 1S state has a numerical uncertainty of 0.8 Hz for hydrogen
and 13 Hz for singly-ionized helium. Resummation and convergence acceleration
techniques that reduce the computer time by about three orders of magnitude
were employed in the calculation. The numerical results are compared to results
based on known terms in the expansion of the self energy in powers of (Z
alpha).Comment: 10 pages, RevTeX, 2 figure
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