Significant deviations previously reported [Phys. Rev. A 36, 5626 (1987)] between experimental and theoretical cross sections for elastic scattering of 88.03-keV γ rays through 125° have been removed. The present paper shows that the S-matrix treatment is successful in predicting γ-ray elastic-scattering cross sections even very close to K-shell thresholds of high-Z elements.

It is shown that the Aharonov-Bohm (AB) effect is a generic feature of any multipole moment moving in an electromagnetic field. Explicit examples of electric and magnetic quadrupole moments are discussed. A way to detect the AB phase of a magnetic quadrupole moment is also provided.

Using a gauge covariant operator technique we deduce the path integral for a charged particle in an arbitrary stationary magnetic field, verifying the ‘‘midpoint rule’’ for the discrete form of the interaction term with the vector potential.

The effect of relativistic corrections in the electron affinities (${\mathit{A}}_{\mathit{e}}$) of the atoms (Li through I) has been determined. The relativistic contributions to the ${\mathit{A}}_{\mathit{e}}$ are negative, except for Cu, Rh, and Ag atoms and are large for some transition-metal atoms. The values of the corrected ${\mathit{A}}_{\mathit{e}}$ have been used in order to estimate the contribution of the correlation energies to the ${\mathit{A}}_{\mathit{e}}$.

The dependence of the mean lifetimes of metastable molecular ions on the vibrational and rotational quantum numbers is determined empirically. From the mean lifetimes calculated using the phase-shift method for the ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^4{}_{}{}^{}$${\mathrm{He}}^{2+}$ and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}_{}^{40}{}_{}{}^{}$${\mathrm{Ar}}^{2+}$ metastable molecular ions, we show that the mean lifetimes of rotational states decrease with angular momentum l approximately as ${\mathrm{\tau }}_{\mathit{l}}$∝${\mathit{e}}^{\mathrm{-}\mathrm{\alpha }\mathit{l}(\mathit{l}+1)}$, and the mean lifetimes of vibrational states decrease with the vibrational quantum number v approximately as ${\mathrm{\tau }}_{\mathit{v}}$∝${\mathit{e}}^{\mathrm{-}\mathrm{\beta }\mathit{v}}$. These empirical results are justified by using the Wentzel-Kramers-Brillouin approximation to estimate the analytic form of the scaling laws.

We have measured experimental triple-differential cross sections for electron-impact ionization of the outer shell of argon at incident energies of 115.8 and 215.8 eV. The experiments have been performed in coplanar symmetric geometry with ${\mathit{E}}_{\mathit{a}}$=${\mathit{E}}_{\mathit{b}}$=50 eV and ${\mathit{E}}_{\mathit{a}}$=${\mathit{E}}_{\mathit{b}}$=100 eV. The results are compared with recent distorted-wave Born-approximation calculations.

The modifications of effective-range theory, necessitated by the long-range nature of interatomic dispersion and relativistic retardation forces, are discussed. A numerical comparison is given of parameters describing ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^3{}_{}{}^{}$He, ${}_{}{}^3{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He, and ${}_{}{}^4{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He scattering at very low energies calculated with several recently published interaction potentials. The effect of relativistic retardation on these parameters and on the calculated binding energies of the ${}_{}{}^4{}_{}{}^{}\mathrm{-}_{}^4{}_{}{}^{}$He dimer is shown. It is demonstrated that all of these quantities are extremely sensitive to the potential. Scattering lengths and effective ranges for the lowest triplet interactions of H-H and D-D are also reported.

Considered as a limiting case of a highly asymmetric two-Coulomb-center problem, the analytic properties of the eigenvalues of the constant of motion allowing separation of variables for a hydrogenlike atom in spheroidal coordinates are studied. Calculations of the positions of the branch points of the eigenvalues in the complex plane of internuclear separations are performed. It is found that they form characteristic series whose limiting points can well be predicted by semiclassical quantization conditions.

The energy loss of silver ions in metallic gadolinium foil at low velocities (2.7–4.3)${\mathit{v}}_0$, where ${\mathit{v}}_0$ is the Bohr velocity, was measured with the Doppler shift technique. The results are about 20% smaller than the predictions of a semiempirical formulation [J. F. Ziegler, J. P. Biersack, and U. L. Littmark, in The Stopping and Ranges of Ions in Solids, edited by J. F. Ziegler (Pergamon, New York, 1985), Vol. 1] for the electronic stopping power.

The energy distributions for 2.5-MeV ${\mathrm{He}}^{+}$ ions incident on thin Si single crystals are studied. Detailed angular scans are taken through the 〈110〉 and 〈100〉 axial directions along the {111} and {110} planar directions as well as perpendicular to the planar directions for Si(110) (0.74- and 1.4-μm-thick) and Si(100) (0.75-μm-thick) samples, respectively. Complex structures in the distributions are observed throughout the angular scans. The experimental distributions are reasonably well reproduced by a Monte Carlo simulation using the semiclassical approximation [N. M. Kabachnik, V. N. Kondratev, and O. V. Chumanova, Phys. Status Solidi B 145, 103 (1988)] for energy loss to core electrons and the two-component free-electron-gas model for energy loss to valence electrons. Systematic deviations between theory and experiment are observed and discussed in terms of an increased penetration depth necessary for ${\mathrm{He}}^{+}$ ions to become fully ionized when channeled.

A simple one-dimensional semiclassical model with a Morse potential is used to investigate the possibility of two-color infrared multiphoton dissociation of vibrationally excited nitrogen oxide. The amplitude ratio effects and adiabatic effects are investigated. Some initial states are found to have thresholds smaller than expected from single-mode considerations and multiple thresholds exist for initial states up to 32.

Both the Wigner function and the field distribution function in the generalized geometric state of the radiation field, which were recently introduced by us [A.-S. F. Obada, S. S. Hassan, R. R. Puri, and M. S. Abdalla, Phys. Rev. A 48, 3174 (1993)], are calculated exactly and examined in both the phase-averaged and the nonaveraged cases.

The collapse-revival phenomenon of Rabi oscillations and the pure-state evolutions of the atomic as well as the field states in the Raman interaction of a pair of effective two-level atoms with a single-mode quantized radiation field are studied with an analytic method. The effects of the relative values of the two-atom–field coupling constants on them are also analyzed.

We have shown how a class of arbitrary two-mode field states can be generated by the injection of three-level Λ-type atoms into a two-mode resonator. An explicit example with SU(2) coherent states has been worked out.

We have done an ab initio calculation based on the Brueckner approximation for the lifetimes of 4${\mathit{p}}^2$P and 3${\mathit{d}}^2$D levels of ${\mathrm{Ca}}^{+}$. The results of the Brueckner approximation differ from experiment by 2.5%. With leading third-order corrections included, our results agree with the latest accurate experiment within a 1% difference.

We propose a scheme for measuring an optical version of the Bell operator, using a generalization of the Hong-Ou-Mandel interferometer. Discrete-mode calculations show this to be sufficient to allow teleportation of the state of polarization of a photon with a conditional efficiency approaching 100%. The feasibility of the scheme is investigated through full broadband calculations.

Radiation tuned to an excited-state transition in dense cesium vapor results in the appearance of induced absorption and fluorescence after delays of up to 5 s, an observation ascribed to a chain reaction of resonant binary collisions initiated by the incident light. Our results occur in a nonlinear regime characterized by high collision rates, which are variable in a controlled fashion at constant vapor density.

Recent convergent close-coupling calculations of the ionization cross section of Na by Bray [Phys. Rev. Lett. 73, 1088 (1994)] are in poor agreement with the experimental determinations, most of which were carried out in the 1960s. We report here a measurement of the ratio of the peak ionization cross section to the cross section for excitation of the $3^2$P state near threshold. By normalizing the latter to the theoretical cross section computed by Moores and Norcross [J. Phys. B 5, 1482 (1972)] and more recently by Trail et al. [Phys. Rev. A 49, 3620 (1994)], we find an ionization cross section in agreement with Bray within 10%.