Atomic Level Shifts Research Articles

Some new results on baryon-antibaryon nearthreshold phenomena

Polarization of antiprotons in pp-scattering at very low momenta is calculated. Obtained small polarization in pp is shown to be due to the existence of P-wave pp quasinuclear resonances. The formula connecting the nuclear scattering length and the atomic level shift is given. Nucleon electromagnetic form-factor near NN threshold is obtained. Its behaviour is shown to be dominantely defined by the NN nuclear interaction in the initial state.

Lifetimes of excited atoms near metal surfaces

We present accurate calculations of the lifetimes and energy shifts of hydrogen and alkali atomic levels near a jellium metal surface. “Complex scaling” of the Schrödinger equation is employed to obtain directly the real and imaginary parts of the atomic resonance energies. Excited atomic levels shift differently with distance and there are many possibilities of level crossings. At such positions the hybridization can be strongly enhanced and lead to states that are oriented towards or away from the surface, with very different lifetimes and non-exponential decay of widths with distance from the surface. Previous calculations of the atomic level widths have not included these facts and typically have overestimated the level widths by several orders of magnitude. We discuss the qualitative consequences of our findings of longer lifetimes and extensive hybridization on the interpretation of neutralization processes in ion-surface collisions. Finally, we show that the presence of a weak lateral corrugation in the surface potential has a similar effect on neutralization as an increased surface temperature.

Atomic-level shifts in a squeezed vacuum.

The energy-level shifts for a multilevel atom interacting with a squeezed vacuum are calculated. The level shifts are made up of two contributions: (i) the ordinary Lamb shift and (ii) a shift due to the squeezed-vacuum intensity spectrum (similar to the blackbody-radiation shifts).

Kemmer-Duffin-Petiau equation approach to pionic atoms.

We lay down the formalism for the treatment of pionic atoms level widths and shifts using the Kemmer-Duffin-Petiau equation. Interactions are introduced in a Lorentz invariant way. An analytical transformation is shown that connects between different sets of interactions. The Kisslinger potential is obtained as a special case of a scalar-tensor optical potential. Results are shown in the accompanying paper.

Nuclei containing an antinucleon.

We have investigated the possibility that a nucleus containing a single antinucleon (N\ifmmode\bar\else\textasciimacron\fi{}) may exhibit some relatively long-lived excited states. Using N\ifmmode\bar\else\textasciimacron\fi{} optical potentials consistent with the available data on p\ifmmode\bar\else\textasciimacron\fi{}-atom level shifts and/or low energy p\ifmmode\bar\else\textasciimacron\fi{}-nucleus scattering, and calculating the complex eigenvalues of the Schr\odinger equation, we find that the annihilation widths of strongly bound (non-Coulomb) N\ifmmode\bar\else\textasciimacron\fi{} states are generally large, as expected, of order \ensuremath{\Gamma}\ensuremath{\approxeq}50\char21{}100 MeV. Some possible exceptions to this may occur when the N\ifmmode\bar\else\textasciimacron\fi{} is bound to a light nuclear core which is not spin and isospin saturated. We obtain cross section estimates for the formation of N\ifmmode\bar\else\textasciimacron\fi{} nuclei via the (p\ifmmode\bar\else\textasciimacron\fi{},p) and (p\ifmmode\bar\else\textasciimacron\fi{},n) reactions on nuclear targets with A=3, 4, and 16.

Scattering Lengths Derived from Atomic Level Shifts in Light Antiprotonic Atoms

Scattering lengths in the systems p̄4He, p̄6Li, p̄7Li, p̄12C, p̄16O, p̄17O, and p̄18O are derived from the measurements of the strong interaction atomic level shifts in the corresponding antiprotonic atoms. The Coulomb corrections to the scattering lengths are evaluated and it is found that they are large.

Analytical calculation of logarithmic mean excitation energies for hydrogen and helium.

The four logarithmic mean excitation energies I(\ensuremath{\nu}), for \ensuremath{\nu}=-1, 0, 1, and 2, have been calculated analytically for hydrogen and helium. They appear in the expressions of total cross section, stopping power, and straggling effect for fast charged particles, and in the expression of the Lamb shift of atomic energy levels. The method is based on a generalization of a method by Dalgarno and Lewis [Proc. R. Soc. London, Ser. A 233, 70 (1956)]. The only input is the wave function of the initial state of the atom (in the present paper only the ground state is considered). For hydrogen the method is rigorous. For helium, Hartree-Fock-type wave functions were used, which is the only approximation of the present method. The accuracy of the method is essentially independent of the value of \ensuremath{\nu}.

Low-energy scattering parameters and atomic level shifts in the p̄ 16O, p̄ 32S and p̄ 40Ca systems

A relationship between the low-energy scattering parameters and atomic level shifts is analyzed in the cases of the p̄ 16O, p̄ 32S and p̄ 40Ca systems. The corresponding scattering lengths are calculated on the basis of energy level shifts evaluated earlier by means of an optical potential.

Kaonic atom level shifts and K−-nucleus scattering lengths

A brief account is given of the systematic differences between π-nuclear and\(\bar K\)-nuclear systems, and of their consequences for the derivation of their scattering lengths from mesic atom data. The scattering lengths for negative kaons on light nuclei are then derived, keeping track of these systematic effects as far as possible, even if in approximate way.

Remote quantum mechanical detection of gravitational radiation

The presumed existence of atomic hydrogen in the vicinity of sources of gravitational radiation suggests its use as a radiation detector. Curvature-induced atomic energy level shifts carry a unique signature and could thus provide for remote detection of gravitational radiation. We investigate the shifts induced by space-time curvature arising from gravitational waves. The effect is studied for both low-lying and highly excited states of atomic hydrogen. Numerical results are quoted for radiation from various sources, including binary star systems, binary neutron stars, binary black holes, collapsing stars, and pulsars. In addition, we provide a theoretical upper limit to the magnitude of the effect. For completeness, we examine the shifts induced in a harmonic oscillator as well as a rigid rotator.

Spontaneous radiative coupling of atomic energy levels

Density-matrix equations of motion derived from Heisenberg picture source-field quantum electrodynamics contain damping constants and frequency shifts which are not associated with a single radiative transition but which instead couple two separate transitions together. In the absence of degeneracies in the atomic levels, these coupling terms are normally neglected when the rotating-wave approximation is invoked. These terms cannot be neglected when there are degeneracies or near degeneracies. In this paper, we interpret the generalized frequency shifts, show how they can be renormalized and included in shifts of atomic energy levels and altered damping constants, and discuss their experimental significance.

Neutron-antineutron oscillations in nuclei

We present calculations of the neutron-antineutron ($n\ensuremath{-}\overline{n}$) annihilation lifetime $T$ in deuterium, $^{16}\mathrm{O}$, and $^{56}\mathrm{Fe}$ in terms of the free-space oscillation time ${T}_{n\overline{n}}$. The coupled Schr\odinger equations for the $n$ and $\overline{n}$ wave functions in a nucleus are solved numerically, using a realistic shell-model potential which fits the empirical binding energies of the neutron orbits, and a complex $\overline{n}$-nucleus optical potential obtained from fits to $\overline{p}$-atom level shifts. Most previous estimates of $T$ in nuclei, which exhibit large variations, are found to be quite inaccurate. When the nuclear-physics aspects of the problem are handled properly (in particular, the finite neutron binding, the nuclear radius, and the surface diffuseness), the results are found to be rather stable with respect to allowable changes in the parameters of the nuclear model. We conclude that experimental limits on $T$ in nuclei can be used to give reasonably precise constraints on ${\ensuremath{\tau}}_{n\overline{n}}$: $Tg{10}^{30} or {10}^{31}$ yr leads to ${\ensuremath{\tau}}_{n\overline{n}}g(1.5\ensuremath{-}2)\ifmmode\times\else\texttimes\fi{}{10}^{7} or (5\ensuremath{-}6)\ifmmode\times\else\texttimes\fi{}{10}^{7}$ sec, respectively.

Anomalous coulomb effect in theK ? p system

Recent measurements of the 2p—1s X-ray line in theK−p atom indicate that the 1s level shift is very different from the theoretical prediction based on the extrapolation from theK−p scattering data. Deloff and Law have suggested that an anomalously large Coulomb effect could be responsible for this discrepancy. We examine this possibility by carrying out an explicit model calculation, using the method by which Sauer demonstrated the possible existence of an anomalously large Coulomb effect in the proton-proton system. Our conclusion is that if there exists an anomalous Coulomb effect which explains theK−p atomic level shift result, then the same effect would cause a serious conflict with theK−p scattering data above threshold.

S-matrix approach to hadronic atom level shifts

It is shown that once the hadron-nucleus scattering problem has been solved, the hadronic atom level shifts and widths can be extracted by continuing the $S$ matrix below threshold.NUCLEAR REACTIONS $S$-matrix theory, hadronic atom complex level shift calculated and correlated with scattering parameters.

Isotope shifts of individual nS and nD levels of atomic potassium

A new method is reported which enables isotope shifts of single atomic levels to be directly extracted from measurements of isotope shifts of transitions between two levels. The method, which is based on the assumption that the isotope shift of a sufficiently high Rydberg level is given solely by the simple Bohr (or normal) mass shift, is demonstrated in an experiment in which isotope shifts of Doppler-free, two-photon transitions (4S-nS, 7<or=n<or=18; 4S-nD, 5<or=n<or=17) in atomic potassium are measured. Appreciable residual isotope shifts are found between 39K and 41K for energy levels lying more than 1000 cm-1 below the atomic ionisation limit.

Low-energy kaon-nucleus interaction

Low-energy kaon-nucleus interaction has been considered in the framework of multiple scattering theory as formulated by Watson and by Kerman, McManus, and Thaler. A kaon-nucleus optical potential of the shape of nuclear density is shown to follow from theory under the assumption that the nuclear excited states may be neglected and that the range of the underlying microscopic $\overline{K}N$ interaction is small in comparison with the nuclear radius. The depth of the effective potential is a nonlinear function of the $\overline{K}N$ scattering lengths and depends upon a single parameter related to the unknown range of the $\overline{K}N$ interaction. This parameter has been adjusted to the available kaonic atom data. The resulting potential has been used to evaluate the kaonic atom level shifts and widths and the calculated quantities are compared with experiment.NUCLEAR REACTIONS Optical potential derived and applied to evaluate kaonic atoms level shifts.

ΣN strong interactions

The recent data of Batty et al. and those of Koch on Σ− atoms level shifts and widths have been analyzed together with the two sets of ΣN scattering lengths extracted by Alexander, Gell, and Stumer to determine if all the data are consistent and also to extract effective ΣN complex potentials. Our results indicate that the Σ− atoms data do not yet distinguish between the two sets of scattering lengths owing to the large uncertainties in level shift and width measurements. However, our best fit set of ΣN potentials preclude the Σ−n or Σ−nn system being bound.

The use of a model potential for the calculation of dynamic polarizabilities, dispersion forces and the light shifts of atomic levels

The form of the model potential of the valence electron suggested by Simons (1971) is used for the calculation of atomic dynamic characteristics given by second-order perturbation theory for the interaction of the atoms with an electromagnetic field. General formulae are derived and the results of numerical calculations in a wide frequency range for the dynamic polarizabilities of ground and excited state of alkali atoms and inert gases are presented. The efficiency of different calculation methods for various light frequencies and principal quantum numbers of the atomic levels is discussed.

Atomic level shifts in laser fields and the space-translation Hamiltonian

Atomic energy level shifts due to the presence of a laser field are calculated to order e 2, and compared with those obtained recently using the space-translation Hamiltonian. Extensive cancellation amongst terms occur; for this reason all contributions to order e 2 must be included in the description of such level shifts.

Atomic level shifts and transition amplitudes in incoming radiation fields

Atomic level shifts and transition amplitudes in incoming radiation fields