A calculation of the spatial distribution of ion emission in the phase-controlled, two-color photodissociation of diatomic molecules in intense, low-frequency laser fields is presented. Using atomic orbitals, we determine the time average of the electronic charge distribution at the critical internuclear separation, the point at which electron localization occurs. We find qualitative agreement with a recent experiment with ${\mathrm{HD}}^{+}$, which shows asymmetry in the counterintuitive direction. We predict that ${\mathrm{H}}_2^{+}$ and lower frequencies will give even better agreement. © 1996 The American Physical Society.

We derive natural representations for two-mode squeezing operators. By natural we mean that the representations are composed by the eigenvectors of either one of the two two-mode quadrature operators for squeezing. The technique of integration within an ordered product of operators provides us with a convenient method of derivation. © 1996 The American Physical Society.

Knowledge of the properties of the exchange-correlation functional in the form 1/λ${\mathit{v}}_{\mathrm{xc}}$([${\mathrm{\rho }}_{\lambda }$],r/λ), where ${\mathrm{\rho }}_{\lambda }$(r)= ${\lambda }^3$ρ(λr), is important when expressing the exchange-correlation energy as a line integral ${\mathit{E}}_{\mathrm{xc}}$[ρ]=${\mathrm{\int }}_0^1$dλ∫dr1/λ${\mathit{v}}_{\mathrm{xc}}$([${\mathrm{\rho }}_{\lambda }$],r/λ) [3ρ(r)+r⋅∇ρ(r)] [R. van Leeuwen and E. J. Baerends, Phys. Rev. A 51, 170 (1995)]. With this in mind, it is shown that in the low-density limit ${\lim }_{\lambda \to 0}$∫ρ(r)${\mathrm{\nabla }}^2$1/λ${\mathit{v}}_{\mathrm{xc}}$([${\mathrm{\rho }}_{\lambda }$],r/λ)${\mathit{d}}^3$ r≤4π∫ρ(r${)}^2$${\mathit{d}}^3$r. This inequality is violated in the local-density approximation. © 1996 The American Physical Society.

Using the diffusion quantum Monte Carlo method, the binding energy of positronium hydroxide (alternatively, the positronium affinity of the hydroxyl radical) has been calculated at a new level of accuracy and found to be 0.63±0.15 eV. Using the same methods, we also calculate the electron affinity of the hydroxyl radical to be 1.86±0.14 eV, which is in agreement with the experimental value. To the authors’ knowledge, this is the only calculation of these quantities for which this essential consistency is demonstrated. © 1996 The American Physical Society.

To confirm the appropriateness of ideas recently put forward [L. F. Errea, C. Harel, H. Jouin, L. Méndez, B. Pons, and A. Riera, Phys. Rev. A 52, R2505 (1995)] concerning the validity of the molecular approach to calculate ionization cross sections, we treat the ${\mathrm{H}}^{+}$ +${\mathrm{H}}^{\mathrm{-}}$ reaction as a widely different benchmark. © 1996 The American Physical Society.

A sharp estimate is given for the amount of Shannon information and expected collision probability. This estimate is valid for all eavesdropping strategies described by a generalized measurement and restricted to the Hilbert space of the one-photon state. The optimal generalized measurement is explicitly given. © 1996 The American Physical Society.

We present experimental and theoretical results for the spatial pattern of forwardly scattered H(n=2,3) atoms created by electron transfer from optically prepared Na(3p) atoms by 2-keV proton impact. The near-resonant H(n=2) and the endoergic H(n=3) channels display dramatically different left-right scattering asymmetries, varying strongly with the initial polarization of the target. The results illuminate current ideas on the role of the internal dynamics for transition propensities in the electron transfer process, including a connection between the collisional behavior of aligned and oriented states. © 1996 The American Physical Society.

The R-matrix method is used to calculate the 3p photoabsorption cross section of ${\mathrm{Mn}}^{+}$ for the photon energy region which contains the giant 3p→3d resonance. Close agreement is found with recent experimental data with regard to the background cross section and for some of the other resonances identified experimentally. In this paper, additional 3${\mathit{p}}^5$3${\mathit{d}}^6$4${\mathit{d}}^7$${\mathit{P}}^{\mathit{o}}$ resonances, which have not been found previously, are identified. © 1996 The American Physical Society.

An extension of a theory of the relaxation, generation, and detection of Zeeman components in the presence of a weak static magnetic field to experiments where hyperfine coherences are also involved is presented. Our study focuses on the geometrical aspects of the optical-microwave double-resonance experiments without considering the transition-profile related phenomena. We determine the coupled evolution equations of the Zeeman and hyperfine components of the atomic density matrix in the irreducible formalism and calculate the stationary solutions to these equations. © 1996 The American Physical Society.

We report a two-photon interference experiment that realizes a postselection-free test of Bell's inequality based on energy-time entanglement. In contrast with all previous experiments of this type, the employed entangled states are obtained without the use of a beam splitter or a short coincidence window to "throw away" unwanted amplitudes. A (95.0±1.4)% interference fringe visibility is observed, implying a strong violation of the Bell inequality. The scheme is very compact and has demonstrated excellent stability, suggesting that it may be useful, for example, in practical quantum cryptography.

Using a merged-beams technique, absolute total electron-capture cross sections have been measured in the thermal energy regime for collisions of ${\mathrm{Si}}^{4+}$ ions with neutral D atoms. State-of-the-art molecular-orbital coupled-channel calculations for the ${\mathrm{Si}}^{4+}$ +H(D) systems are compared to the measurements on an absolute scale. Both the existence of a surprisingly large kinematic isotope effect and an observed sharp low-energy increase of the cross section are attributed to trajectory effects due to an attractive ion-induced dipole.

We excited a special class of states of a three-body Coulomb system, populating double Rydberg states of the type $\mathrm{Ngng}$ [$N=5-9\mathrm{}$, $n\gg N$ where $N\left(n\right)\mathrm{}$ is the principal quantum number of the inner (outer) valence electron] in Ba with both valence electrons in non-core-penetrating orbits with the same orbital angular momentum. Electron correlation effects manifest themselves by the appearance of additional $\mathrm{Nhnl}$ resonances, a rapid increase of the observed quantum defects with $N$, as well as a significant decrease of the autoionization rate for $N=9\mathrm{}$.

We observed the phase shift of the atomic wave function induced from the dc Stark effect using an atom interferometer comprised of four copropagating traveling laser beams. We calculated the interference signal for the interferometer in the case of a thermal atomic beam. By comparing the observed interference fringes with the calculated ones, the difference between the polarizabilities of the ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$ state and the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ state of calcium was obtained to be $\alpha \left({}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}\right)-\alpha \left({}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}\right)=(13.4\mathrm{}\pm 2.0)\times {10}^{-24\mathrm{}}$ ${\mathrm{cm}}^3$. This value was consistent with that deduced from the Stark frequency shift.

We show that probe resonance fluorescence measurements on a single trapped ion at the node of a pulsed optical standing wave can be used to tomographically reconstruct the initial vibrational state of the ion. The Wigner function describing the density matrix of the initial vibrational state is determined by measuring the population inversion of the ion at the end of the standing-wave pulse over a range of free evolution times and pulse strengths.

In view of two recent Bose-Einstein condensation experiments, we have calculated the magnetic-dipolar decay-rate constants of the atomic density for the doubly polarized state in ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$ and ${}_{}{}^{85}{}_{}{}^{}\mathrm{Rb}$, and for the highest state of the lower hyperfine manifold in ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$.

Wave packets comprising a superposition of very-high-lying Rydberg states have been created using a half-cycle pulse (HCP). The properties of the wave packet are probed using a second HCP that is applied following a variable time delay. The second pulse ionizes a fraction of the atoms and the survival probability exhibits pronounced oscillations that are associated with the quasiperiodic evolution of the wave packet. Good agreement is found between the experimental data and the results of a classical trajectory Monte Carlo simulation demonstrating that, for the times investigated, classical-quantum correspondence holds and quantum corrections are negligible.

The study and control of molecular dynamics through the use of femtosecond laser techniques require an understanding of various orders of molecular wave-packet phenomena such as revivals. We present the observation of fractional revivals in a vibrational wave packet: the $B$ state of the ${\mathrm{Br}}_2$ molecule. Fractional revivals occur in anharmonic systems at characteristic times in the nonclassical regime when, due to dephasing between vibrational eigenstates, the wave packet partially localizes into sub-wave-packets. Half and quarter revivals were clearly observed, as well as indications of one-sixth revivals.