445 research outputs found
Hyperfine structure of S states in Li and Be^+
A large-scale configuration-interaction (CI) calculation is reported for the
hyperfine splitting of the 2^2S and 3^2S states of ^7Li and ^9Be^+. The CI
calculation based on the Dirac-Coulomb-Breit Hamiltonian is supplemented with a
separate treatment of the QED, nuclear-size, nuclear-magnetization
distribution, and recoil corrections. The nonrelativistic limit of the CI
results is in excellent agreement with variational calculations. The
theoretical values obtained for the hyperfine splitting are complete to the
relative order of \alpha^2 and improve upon results of previous studies.Comment: 4 pages, 2 table
Field-theory calculation of the electric dipole moment of the neutron and paramagnetic atoms
Electric dipole moments (edms) of bound states that arise from the
constituents having edms are studied with field-theoretic techniques. The
systems treated are the neutron and a set of paramagnetic atoms. In the latter
case it is well known that the atomic edm differs greatly from the electron edm
when the internal electric fields of the atom are taken into account. In the
nonrelativistic limit these fields lead to a complete suppression, but for
heavy atoms large enhancement factors are present. A general bound-state field
theory approach applicable to both the neutron and paramagnetic atoms is set
up. It is applied first to the neutron, treating the quarks as moving freely in
a confining spherical well. It is shown that the effect of internal electric
fields is small in this case. The atomic problem is then revisited using
field-theory techniques in place of the usual Hamiltonian methods, and the
atomic enhancement factor is shown to be consistent with previous calculations.
Possible application of bound-state techniques to other sources of the neutron
edm is discussed.Comment: 21 pages, 5 figure
Two-Loop Bethe Logarithms for non-S Levels
Two-loop Bethe logarithms are calculated for excited P and D states in
hydrogenlike systems, and estimates are presented for all states with higher
angular momenta. These results complete our knowledge of the P and D energy
levels in hydrogen at the order of alpha^8 m_e c^2, where m_e is the electron
mass and c is the speed of light, and scale as Z^6, where Z is the nuclear
charge number. Our analytic and numerical calculations are consistent with the
complete absence of logarithmic terms of order (alpha/pi)^2 (Z alpha)^6 ln[(Z
alpha)^(-2)] m_e c^2 for D states and all states with higher angular momenta.
For higher excited P and D states, a number of poles from lower-lying levels
have to subtracted in the numerical evaluation. We find that, surprisingly, the
corrections of the "squared decay-rate type" are the numerically dominant
contributions in the order (alpha/pi)^2 (Z alpha)^6 m_e c^2 for states with
large angular momenta, and provide an estimate of the entire B_60-coefficient
for Rydberg states with high angular momentum quantum numbers. Our results
reach the predictive limits of the quantum electrodynamic theory of the Lamb
shift.Comment: 14 pages, RevTe
Recoil corrections in the hydrogen isoelectronic sequence
A version of the Bethe-Salpeter equation appropriate for calculating recoil
corrections in highly charged hydrogenlike ions is presented. The nucleus is
treated as a scalar particle of charge Z, and the electron treated
relativistically. The known recoil corrections of order are
derived in both this formalism and in NRQED
Lamb shift in muonic deuterium atom
We present new investigation of the Lamb shift (2P_{1/2}-2S_{1/2}) in muonic
deuterium (mu d) atom using the three-dimensional quasipotential method in
quantum electrodynamics. The vacuum polarization, nuclear structure and recoil
effects are calculated with the account of contributions of orders alpha^3,
alpha^4, alpha^5 and alpha^6. The results are compared with earlier performed
calculations. The obtained numerical value of the Lamb shift 202.4139 meV can
be considered as a reliable estimate for the comparison with forthcoming
experimental data.Comment: 24 pages, 11 figures. arXiv admin note: text overlap with
arXiv:hep-ph/061229
Three-Loop Radiative-Recoil Corrections to Hyperfine Splitting in Muonium
We calculate three-loop radiative-recoil corrections to hyperfine splitting
in muonium generated by the diagrams with the first order electron and muon
polarization loop insertions in graphs with two exchanged photons. These
corrections are enhanced by the large logarithm of the electron-muon mass
ratio. The leading logarithm squared contribution was obtained a long time ago.
Here we calculate the single-logarithmic and nonlogarithmic contributions. We
previously calculated the three-loop radiative-recoil corrections generated by
two-loop polarization insertions in the exchanged photons. The current paper
therefore concludes calculation of all three-loop radiative-recoil corrections
to hyperfine splitting in muonium generated by diagrams with closed fermion
loop insertions in the exchanged photons. The new results obtained here improve
the theory of hyperfine splitting, and affect the value of the electron-muon
mass ratio extracted from experimental data on the muonium hyperfine splitting.Comment: 27 pages, 6 figures, 7 table
Radiative Corrections to One-Photon Decays of Hydrogenic Ions
Radiative corrections to the decay rate of n=2 states of hydrogenic ions are
calculated. The transitions considered are the M1 decay of the 2s state to the
ground state and the E1(M2) decays of the and states to
the ground state. The radiative corrections start in order , but the method used sums all orders of . The leading
correction for the E1 decays is calculated and compared
with the exact result. The extension of the calculational method to parity
nonconserving transitions in neutral atoms is discussed.Comment: 22 pages, 2 figure
Third-order many-body perturbation theory calculations for the beryllium and magnesium isoelectronic sequences
Relativistic third-order MBPT is applied to obtain energies of ions with two
valence electrons in the no virtual-pair approximation (NVPA). A total of 302
third-order Goldstone diagrams are organized into 12 one-body and 23 two-body
terms. Only third-order two-body terms and diagrams are presented here, owing
to the fact that the one-body terms are identical to the previously studied
third-order terms in monovalent ions. Dominant classes of diagrams are
identified. The model potential is a Dirac-Hartree-Fock potential,
and B-spline basis functions in a cavity of finite radius are employed in the
numerical calculations. The Breit interaction is taken into account through
second order of perturbation theory and the lowest-order Lamb shift is also
evaluated. Sample calculations are performed for berylliumlike ions with Z =
4--7, and for the magnesiumlike ion P IV. The third-order energies are in
excellent agreement with measurement with an accuracy at 0.2% level for the
cases considered. Comparisons are made with previous second-order MBPT results
and with other calculations. The third-order energy correction is shown to be
significant, improving second-order correlation energies by an order of
magnitude
Hadronic Vacuum Polarization Contribution to the Muonium Hyperfine Splitting
We discuss hadronic effects in the muonium hyperfine structure and derive an
expression for the hadronic contribution to the hfs interval in form of the
one-dimensional integral of the cross section of e+e- annihilation into
hadrons. Higher-order hadronic contributions are also considered
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