334 research outputs found
Vacuum polarization calculations for hydrogenlike and alkalilike ions
Complete vacuum polarization calculations incorporating finite nuclear size
are presented for hydrogenic ions with principal quantum numbers n=1-5.
Lithiumlike, sodiumlike, and copperlike ions are also treated starting with
Kohn-Sham potentials, and including first-order screening corrections. In both
cases dominant Uehling terms are calculated with high accuracy, and smaller
Wichmann- Kroll terms are obtained using numerical electron Green's functions.Comment: 23 pages, 1 figur
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
Electron Self Energy for Higher Excited S Levels
A nonperturbative numerical evaluation of the one-photon electron self energy
for the 3S and 4S states with charge numbers Z=1 to 5 is described. The
numerical results are in agreement with known terms in the expansion of the
self energy in powers of Zalpha.Comment: 3 pages, RevTeX, to appear in Phys. Rev.
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
Hadronic Vacuum Polarization and the Lamb Shift
Recent improvements in the determination of the running of the fine-structure
constant also allow an update of the hadronic vacuum-polarization contribution
to the Lamb shift. We find a shift of -3.40(7) kHz to the 1S level of hydrogen.
We also comment on the contribution of this effect to the determination by
elastic electron scattering of the r.m.s. radii of nuclei.Comment: 7 pages, latex, 1 figure -- Submitted to Phys. Rev. A -- epsfig.sty
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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
The effect of pulse crop rotation and controlled-release urea on the N accumulation and end-use quality of CWRS wheat
Non-Peer ReviewedSpring wheat was grown at Carman in 2000 and 2001, and at Brandon, MB, in 2001, on field pea
and flax stubble at three rates of N (0, 30, and 90 kg N ha-1) supplied as ammonium nitrate (AN)
or controlled release urea (CRU), a polyurethane-coated urea. Wheat was grown in 2000 and
2001 at Swift Current, SK, on field pea and durum stubble at three rates of urea N (34, 50, and
78 kg N ha-1) based on soil test recommendations. Wheat grown on field pea stubble (P-W) had
higher protein content (PC) than wheat grown on flax/durum stubble (F-W) at four of the five
sites evaluated. Contrary to expectations, post-anthesis apparent net mineralized N and
proportion of total N uptake were higher for F-W compared to P-W at the Carman 2000 and
Brandon 2001 sites. Differences between fertilizer N sources were minor. Breadmaking quality
of the wheat end-use quality was also assessed. At the same flour protein content (FPC), P-W
had a shorter Mixograph dough development time, work input-to-peak, dough strength index,
and breakdown resistance, and also tended to be more extensible than F-W
Lamb Shift of Laser-Dressed Atomic States
We discuss radiative corrections to an atomic two-level system subject to an
intense driving laser field. It is shown that the Lamb shift of the
laser-dressed states, which are the natural state basis of the combined
atom-laser system, cannot be explained in terms of the Lamb shift received by
the atomic bare states which is usually observed in spectroscopic experiments.
In the final part, we propose an experimental scheme to measure these
corrections based on the incoherent resonance fluorescence spectrum of the
driven atom.Comment: 4 pages, 1 figure, submitted for publicatio
Relativistic and Radiative Corrections to the Mollow Spectrum
The incoherent, inelastic part of the resonance fluorescence spectrum of a
laser-driven atom is known as the Mollow spectrum [B. R. Mollow, Phys. Rev.
188, 1969 (1969)]. Starting from this level of description, we discuss
theoretical foundations of high-precision spectroscopy using the resonance
fluorescence light of strongly laser-driven atoms. Specifically, we evaluate
the leading relativistic and radiative corrections to the Mollow spectrum, up
to the relative orders of (Z alpha)^2 and alpha(Z alpha)^2, respectively, and
Bloch-Siegert shifts as well as stimulated radiative corrections involving
off-resonant virtual states. Complete results are provided for the hydrogen
1S-2P_{1/2} and 1S-2P_{3/2} transitions; these include all relevant correction
terms up to the specified order of approximation and could directly be compared
to experimental data. As an application, the outcome of such experiments would
allow for a sensitive test of the validity of the dressed-state basis as the
natural description of the combined atom-laser system.Comment: 20 pages, 1 figure; RevTe
-invariant two-fermion Dirac equation with extended hyperfine operator
For the S-states of muonium and positronium, the hyperfine shifts to the
order of a recently derived two-fermion equation with explicit -invariance are checked against the results of a nonrelativistic reduction,
and the leading shifts are calculated. An additional hyperfine
operator is discovered which can milden the singularity for of the
Dirac hyperfine operator, such that the resulting extended operator can be used
nonperturbatively. The binding correction to magnetic moments is mentioned
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