Stapp [preceding Comment, Phys. Rev. A 60, 2595 (1999)] has argued that my criticism of his nonlocality proof is wrong. I point out that counterfactual arguments are fraught with dangers, and that any such claim should use them in a conservative manner. A reanalysis of his claims continues to lead me to the conclusion that the nonlocality of quantum mechanics remains unproven.

When a fermion-system ground state is examined in the grand ensemble, particle density is determined uniquely by local chemical potential except when an additional fermion is in the process of appearing. Conversely, the chemical potential is uniquely determined by the density profile except when there are an integer number of particles, but is then necessarily linear in a two-state mixing parameter. This linear dependence has immediate consequences, one of which has elicited prior commentary.

By introducing the shape-invariant Lie algebra spanned by the supersymmetric ladder operators plus the identity operator, we generate a discrete complete orthonormal basis for the quantum treatment of the one-dimensional Morse potential. In this basis, which we call the pseudo-number-states, the Morse Hamiltonian is tridiagonal. Then we construct algebraically the continuous overcomplete set of coherent states for the Morse potential in close analogy with the harmonic oscillator. These states coincide with a class of states constructed earlier by Nieto and Simmons [Phys. Rev. D 20, 1342 (1979)] by using the coordinate representation. We also give the unitary displacement operator creating these coherent states from the ground state.

We have performed a relativistic many-body calculation of the off-diagonal hyperfine interaction mixing amplitude $M_{\mathrm{hf}}$ for the $6s-7s$ transition in atomic cesium. The ab initio result $M_{\mathrm{hf}}=0.8070\mathrm{}\left(73\right)\mathrm{}\times {10}^{-5}|{\mu }_{\mathrm{B}}/c|$ is in excellent agreement with a previous semiempirical value $M_{\mathrm{hf}}=0.8094\mathrm{}\left(20\right)\mathrm{}\times {10}^{-5}|{\mu }_{\mathrm{B}}/c|.$

We evaluate the contribution of the quasifree (QF) mechanism to the ratio of double-to-single ionization by one photon. This mechanism is expected to take place in the interaction of a high-energy photon with an atom, and results in the mutual sharing of the photon momentum by two electrons, with small momentum transferred to the nucleus. In this case the electrons should be ejected in nearly opposite directions, sharing the energy nearly symmetrically. By using retardation, we show that the QF contribution displays a ${\omega }^{-5/2}$ energy dependence, in contrast to the well-known ${\omega }^{-7/2}$ energy dependence of the shake-off term. Our calculation shows that the QF mechanism does not give a leading contribution to the ratio of double-to-single ionization for keV photon energies, and is smaller than previously predicted.

A measurement of the fine-structure properties of the atomic chlorine $2p$ subshell has been carried out using electron spectrometry in conjunction with synchrotron radiation. We observe eight of the ten photopeaks predicted for this open-shell atom. Binding energies, relative intensities, and angular distribution parameters are reported for an incident photon energy of 245 eV. Experimental binding energies and intensities are in reasonable agreement with our calculations using a Slater-Condon superposition-of-configuration method.

Structures, likely due to negative-ion resonances, are predicted in the electron-impact-induced alignment of the ${\mathrm{Na}}^{*}{(2p}^5{3s}^2{)}^2{P}_{3/2}$ autoionizing state near the excitation threshold. The predictions are supported by measurements of the alignment via the anisotropic emission of the autoionization electrons in the impact energy range from threshold to 80 eV. Our R-matrix (close-coupling) calculations successfully reproduce the broad-scale energy dependence of the alignment that, above the resonance region, is found to be similar to that for the valence-excited ${(2p}^5{3s)}^1{P}_1$ state in Ne.

A sequence of two identical ultrashort laser pulses creates quantum interferences in an atom. In the weak-field regime, the observed beats between interferences arising from various transitions are not a conclusive signature of wave-packet creation. On the contrary, in the saturation regime, the appearance of slow modulation is. We report on the observation of such modulations in atomic potassium in this field regime. The results are explained within the bright-state–dark-state framework. The wave packet corresponds to the precession of the electronic spin and orbital angular momentum.

Radio-frequency-induced evaporative cooling of ${}^{87}\mathrm{Rb}$ atoms in the $F=2,$ $m=2\mathrm{}$ ground state in a magnetic trap with a high bias field is found to be hampered, and eventually interrupted, by the presence of nonlinear Zeeman shifts. An experiment studying evaporation at a fixed adjustable rf frequency was used to illustrate this effect. These nonlinear shifts prevent us from reaching quantum degeneracy in the $F=2,$ $m=2\mathrm{}$ ground state; however, evaporation in the $F=1,$ $m=-1$ ground state is not adversely affected, and we can produce a Bose-Einstein condensate (BEC). Our analysis shows that this effect can play a role in many BEC experiments.

The limit of $ħk\gamma /2\mathrm{}$ imposed on the magnitude of radiative forces by the spontaneous decay rate $\gamma$ of the excited state can be overcome by coherent control of the momentum exchange between atoms and the light field. This can be implemented with two light beams, each containing two frequencies whose phases, amplitudes, and frequency difference are carefully chosen. We have made precise measurements of the extremely large magnitude and velocity range of this bichromatic force, and have shown that its velocity dependence near the edge of its range is suitable for atomic beam slowing and laser cooling. Our measurements have corroborated various models and calculations of this bichromatic force.

We report an experimental study of the Wannier-Stark fan and the fractional Wannier-Stark ladder using laser-cooled sodium atoms in an accelerating one-dimensional standing wave of light. We prepare the atoms in the lowest motional band of the optical lattice and then impose a constant acceleration. A weak oscillatory component is added to the acceleration in order to resonantly drive interband transitions, and the number of atoms that remain in the lowest band is measured as a function of the probe frequency. The spectrum is characterized by a ladder of resonances spaced by the atomic Bloch oscillation frequency ${\omega }_B.$ When an additional, strong ac component at frequency $\Omega$ is added, a fractional ladder is observed with a spacing related to the electric matching ratio $\Omega /{\omega }_B.$

Experimental photoelectron spectra, with high resolution in both kinetic energy and intensity, have been obtained and compared to a high-precision integration of the Schrödinger equation for photoelectron kinetic-energy yields in argon. We find exceptional quantitative agreement between data and calculation over a wide range of kinetic energies and peak laser intensities. In this paper we conclusively show that the single active electron model describes the physics of high-intensity photoionization to a high degree of accuracy. Furthermore, while multiple electrons may be ionized, multielectron effects appear to be completely absent from above-threshold-ionization photoelectron spectra.

We theoretically study the propagation of light in a Fermi-Dirac gas in the presence of a superfluid state. BCS pairing between atoms in different spin levels increases the optical linewidth and line shift of a quantum degenerate Fermi-Dirac gas already at very low densities and introduces a collisional local-field shift that may dramatically dominate the Lorentz-Lorenz shift. These optical properties could possibly signal the presence of the superfluid state and determine the value of the BCS order parameter.

We discuss dissipative dynamics of a vortex state in a trapped Bose-condensed gas at finite temperature and draw a scenario of decay of this state in a static trap. The interaction of the vortex with the thermal cloud transfers energy from the vortex to the cloud and induces the motion of the vortex core to the border of the condensate. Once the vortex reaches the border, it immediately decays through the creation of excitations. We calculate the characteristic lifetime of a vortex state and address the question of how the dissipative dynamics of vortices can be studied experimentally.

We report on the demonstration of Berry’s phase in an atomic state interacting with a laser field. We draw an analogy between this system and that of a spin interacting with a directionally varying magnetic field. This allows us to identify an effective magnetic quantum number for the atom-light system that governs the maximum Berry phase the atomic state can acquire. We realize two systems that have different effective magnetic quantum numbers, and use a recently developed atom interferometer to make measurements of Berry’s phase.

By solving numerically the tunneling quantum dynamics between two trapped Bose-Einstein condensates (BEC’s), we find two distinct time scales. On the short time scale, we recover semiclassical predictions such as “macroscopic quantum self-trapping” and the “amplitude transition,” first studied in the polaron context, and the $“\pi$ states,” previously discovered in the context of BEC’s. On a much longer time scale, quantum dynamics shows that self-trapping is destroyed in contrast to semiclassical behavior. However, this time scale increases exponentially with the total number of condensate atoms, indicating that self-trapping and $“\pi$ states” would be relevant and experimentally observable in the tunneling of BEC’s.

A method for calculating the redistribution of resonance radiation in hot, dense plasmas is developed by extending the frequency fluctuation model (FFM). This model was originally designed as a numerical procedure for the calculation of the spectral shape of Stark-broadened lines emitted by multielectron ions and has been particularly useful in computations accounting for the ion dynamics effect. The FFM is based on a numerical technique that replaces the primitive inhomogeneous Stark component contributions to the linear response line shape with the observable radiative channels. These channels can be viewed as equivalent to a system of microfield dressed two-level radiators, the Stark-dressed transitions (SDT), which emit a set of spectral lines that reproduce the main features of the first-order radiative properties of the emitter. The mixing of these transitions through a stochastic process is equivalent to random fluctuations of the local ion microfield. The SDT form the basis for the extension of the FFM to the computation of nonlinear response functions. The theory of the second-order radiative redistribution function is reviewed and examples are given.

We present a complex-coordinate rotation calculation of the doubly excited high-angular-momentum $(L>~3)$ resonance states of the positronium negative ion, ${\mathrm{Ps}}^{-},$ associated with the $N=3,$ $N=4\mathrm{}$, and $N=5\mathrm{}$ thresholds of the Ps atom. Products of Slater-type orbitals are used to represent the two-electron wave functions. For the Ps $N=5\mathrm{}$ threshold, states with angular momentum up to $L=8\mathrm{}$ are calculated. Results for doubly excited intrashell states are used to construct the supermultiplet structures of the energy levels of ${\mathrm{Ps}}^{-},$ revealing rotational and vibrational series similar to those for an XYX triatomic molecule.