Internal emission and recoil corrections on radiative π+-proton scattering

Along the line of a previous work we calculate the π⁺?P radiative scattering cross section at the incoming π⁺ energies of T_π = 298, 269, and 324 MeV. The results of the calculation turn out to be in very good agreement with the experimental data for all the energies, showing the great importance of the rescattering and recoil corrections given by the proton motion.     

Proton radius,Darwin-Foldy term and radiative corrections

We discuss the role of the so-called Darwin-Foldy term in the evaluation of the proton and deuteron charge radii from atomic hydrogen spectroscopy and nuclear scattering data. The question of whether this term should be included or excluded from the nuclear radius has been controversially discussed in the literature. We attempt to clarify which literature values correspond to which conventions. A detailed discussion of the conventions appears useful because a recent experiment [R. Pohl et al., Nature 466, 213 (2010)] has indicated that there is a discrepancy between the proton charge radii inferred from ordinary (“electronic”) atomic hydrogen and muonic hydrogen. We also investigate the role of quantum electrodynamic radiative corrections in the determination of nuclear radii from scattering data, and propose a definition of the nuclear self energy which is compatible with the subtraction of the radiative corrections in scattering experiments.     

Optical bistability at low light level due to collective atomic recoil

We demonstrate optical nonlinearities due to the interaction of weak optical fields with the collective motion of a strongly dispersive ultracold gas. The combination of a recoil-induced resonance in the high gain regime and optical waveguiding within the dispersive medium enables us to achieve a collective atomic cooperativity of 275+/-50 even in the absence of a cavity. As a result, we observe optical bistability at input powers as low as 20 pW. The present scheme allows for dynamic optical control of the dispersive properties of the ultracold gas using very weak pulses of light. The experimental observations are in good agreement with a theoretical model.     

Optically-induced energy level shifts for intermediate intensities

We report measurements of optically-induced energy level shifts produced by nonresonant light at intermediate intensities in atomic sodium vapor. The intensity dependence of the shifts departs substantially from the linear behavior predicted by 2nd order perturbation theory. The behavior is in good agreement with more exact calculations and yields a value of 0.10 for the 3P_{$\text{3}\text{2}$}?4D oscillator strength.     

QCD radiative correction to zero recoil sum rules for heavy flavor transitions in the small velocity limit

We consider the small velocity sum rules for heavy flavour semileptonic transitions that are used to estimate the zero recoil values of semileptonic heavy flavour form factors. We analyze the complete O(α _s) radiative correction to these sum rules. The corrections are universal and influence all “model-independent” bounds previously derived for semileptonic form factors at zero recoil. Supported in part by the BMFT, Germany, under contract 06MZ730     

Chemisorption-induced Pt 4f surface core level shifts

Soft X-ray photoemission experiments have led to the unambiguous observation of a metal surface core level ($\text{Pt}\text{4}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$) shift, due to an adsorbate (CO), to a binding energy larger than the bulk binding energy. The $\text{4}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ clean (110) surface component, with a binding energy 0.35 ± 0.02 eV lower than the bulk, is shifted by 1.06 ± 0.04 eV towards higher binding energy upon CO chemisorption. The lack of significant changes in the bulk component indicates the localized nature of the CO-Pt surface bonding.     

Elastic scattering of slow electrons and level shifts in Ar

The differential and total cross sections for elastic scattering of slow electrons and the energy shifts of hole levels in Ar have been obtained using the self-energy part of the single-particle Green function found in the random phase approximation with exchange.     

Core level binding energy shifts between free and condensed atoms

Assuming a fully screened final state (in the metallic case) and using the (Z + 1) approximation and a Born—Haber cycle we calculate the shift in the core level binding energy between the free atom and its metallic state. The agreement with known experimental shifts is shown to be very good. Utilization of the present method can for example give accurate core level binding energies for those free atoms where such data only exist for the metallic phase.     

Empirical formula for energy level shifts of pionic atoms

An empirical formula for energy level shifts of pionic atoms is proposed. Numerical results show remarkably good agreement with experimental data. We predict energy level shifts and widths for pionic deuterium, tritium and helium. With these values, scattering lengths of π-d, π-t and π-³He are also calculated. The results are (in fm) ?0.083 + 0.024 i, ?0.287 + 0.028 i and 0.067 + 0.035 i, respectively.     

On the relation between protonium level shifts and nucleon-antinucleon scattering amplitudes

We study the Coulomb and threshold corrections to the low-energy scattering parameters for the proton-antiproton system, with numerical examples based on current optical models. Some commonly used expressions are shown to be inconsistent with our results. We check that the Trueman formula is valid for the level shifts of protonium, provided one takes properly into account the Coulomb corrections to the scattering lengths and volumes.     

Cavity-induced damping and level shifts in a wide aperture spherical resonator

We calculate explicitly the space dependence of the radiative relaxation rates and associated level shifts for a dipole placed in the vicinity of the center of a spherical cavity with a large numerical aperture and a relatively low finesse. In particular, we give simple and useful analytic formulas for these quantities, that can be used with arbitrary mirrors transmissions. The vacuum field in the vicinity of the center of the cavity is actually equivalent to the one obtained in a microcavity, and this scheme allows one to predict significant cavity QED effects.     

Hydrogen atom and its energy level shifts in de Sitter universe

We investigate the influence of a cosmological constant on the energy levels of a one-electron atom in Fermi normal coordinates. The non-relativistic nS, nP energy levels and the relativistic 1S _1/2, 2S _1/2, 2P _1/2, 2P _3/2 energy levels are calculated in terms of the Riemann tensor. These energy level shifts are non-zero which indicate that the first order gravitational perturbations can partly remove the degeneracy of the studied states in de Sitter space. We show that it is not possible to use the hydrogen atom as a probe of background curvature of the universe. In the second order of perturbation, for 1S state, an upper limit for the energy shifts is obtained.     

Numerical evaluation of the 1S12-state radiative level shift

The one-photon self-energy radiative level shift for an electron in a Coulomb potential is evaluated numerically for the $\text{1S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ state. The evaluation is done for values of the nuclear charge Z = 10, 20,…, 110. The errors in the values obtained are estimated to be less than 0.1 %. The results are compared with the results of previous calculations. The evaluation is based on the expressions given in the preceding paper.     

World-line techniques for resumming gluon radiative corrections at the cross-section level

We employ the Polyakov world-line path-integral version of QCD to identify and resum at leading perturbative order enhanced radiative gluon contributions to the Drell-Yan type ( pair annihilation) cross-sections. We emphasize that this is the first time that world-line techniques are applied to cross-section calculations. Received: 10 June 2002 / Published online: 31 October 2002 RID="a" ID="a" e-mail: akaranik@cc.uoa.gr RID="b" ID="b" e-mail: cktorid@cc.uoa.gr RID="c" ID="c" e-mail: stefanis@tp2.ruhr-uni-bochum.de     

Graser with recoil

The role of the Mössbauer Effect in the gamma-ray laser is frequently portrayed as being based solely on the capacity for recoilless emission and absorption of radiation. This role is reexamined. The possibility of a graser allowing recoil is then discussed.     

Maximum gravitational recoil

Recent calculations of gravitational radiation recoil generated during black-hole binary mergers have reopened the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. Here we report the first systematic study of gravitational recoil of equal-mass binaries with equal, but counteraligned, spins parallel to the orbital plane. Such an orientation of the spins is expected to maximize the recoil. We find that recoil velocity (which is perpendicular to the orbital plane) varies sinusoidally with the angle that the initial spin directions make with the initial linear momenta of each hole and scales up to a maximum of approximately 4000 km s-1 for maximally rotating holes. Our results show that the amplitude of the recoil velocity can depend sensitively on spin orientations of the black holes prior to merger.     

Relative core level shifts in XPS: a theoretical study

The commonly used assumption that all core levels exhibit the same chemical shift is examined using Dirac–Fock electronic structure calculations for a wide range of free atoms and ions. In contrast to experimental results for molecules and solids, the calculated core level shifts are found to be almost uniform. The role of the Madelung potential in exaggerating relative core level shifts in solids and molecules is discussed. Calculated results are found to agree well with the most reliable experimental data.