We have observed a heteronuclear trap loss rate for a mixture of trapped ${}^{39}\mathrm{K}$ and ${}^{85}\mathrm{Rb}$ atoms. Our results indicate that hyperfine changing collision and radiative escape dominate in the low and high intensity regimes, respectively. They are also consistent with radiative escape taking place with the participation of the doubly excited state potential $({\mathrm{K}}^{*}-{\mathrm{Rb}}^{*}).\mathrm{}$ A Gallagher-Pritchard model taking into account the doubly excited channel was implemented, reproducing the experimental results well qualitatively. The values obtained for the cross species trap loss indicate possibilities of future experiments with this mixture.

We present a complex-scaling generalized pseudospectral method for accurate and efficient treatment of resonance states in two-center molecular systems, involving optimal nonuniform grid discretization of the Hamiltonian in prolate spheroidal coordinates. The procedure is applied to the first converged non-Hermitian Floquet study of multiphoton ionization of molecular ions in intense low-frequency (1064 nm) laser fields. We explore the underlying mechanism responsible for the ionization enhancement of ${\mathrm{H}}_2^{+}$ at some critical internuclear distances. Several features of the complex quasienergy states are observed. A detailed analysis of the nature and dynamical behavior of these quasienergy states reveals that the ionization enhancement is mainly due to the effect of charge-resonance-enhanced multiphoton resonances of the $1{\sigma }_g$ and $1{\sigma }_u$ states with excited electronic states at some particular internuclear distances. These “critical” distances depend on the details of molecular electronic structure and the laser frequency and intensity used in the study.

We study the resonance Raman scattering of light from a three-level atom embedded in a photonic band-gap material or in a frequency dispersive medium whose photon spectrum exhibits a gap due to photon coupling to medium excitations such as excitons and optical phonons. We demonstrate that the one-particle spectrum of the system consists of either a continuous part with energy lying outside the gap or a single discrete mode with energy lying inside the gap. The discrete mode, which occurs when both of the allowed atomic transitions of the $\Lambda$ configuration lie inside the gap, can be treated as a photon-atom bound state in which the radiation is localized in the vicinity of the atom. In the case of the continuous spectrum, the Rayleigh and Stokes lines are shifted as well as narrowed (or broadened) as the corresponding transition frequencies are shifted relative to the upper band edge, providing a distinctive experimental signature of atom-photon interactions near a photonic band edge.

We analyze nonrelativistic quantum measurement of the time average of the particle’s coordinate, $X\equiv t^{-1}{\int }_0^t{x(t}^{\prime }{)dt}^{\prime }.$ The measurement amplitude is constructed by restricting the Feynman path integral to paths with the required value of X. The resulting decomposition of the Schrödinger wave function determines the type of meter needed to measure X. We show that such meter can be realized as a magnetic moment traveling with the particle in a magnetic field whose magnitude linearly changes with x. Weak and strong measurement regimes are discussed.

Photoion yields of ${\mathrm{Ne}}^{4+}$ from ${\mathrm{Ne}}^{3+}$ ions were successfully measured in the region of the $1\overrightarrow{s}2p$ autoionizing resonance by a photon-ion merged-beam technique. A broad structure centered at 864.5 eV, which is composed of several transitions, was observed in the photoion-yield spectrum. The spectrum was analyzed with the results of multiconfiguration Dirac-Fock calculations. The calculations revealed that the lines contained in the broad structure can be attributed to possible transitions from the ${2s}^2{2p}^3{}^4{S}_{3/2},$ ${}^2{D}_{3/2},$ and ${}^2{D}_{5/2}$ initial levels. The calculated spectrum satisfactorily shows an overall agreement with the experimental one.

Light-atom scattering off a hard wall is studied with consideration of electron transitions initiated by the collision. It is shown that this problem can be solved analytically in the framework of Masel, Merrill, and Miller’s approach [Phys. Rev B 12, 5545 (1975)]. Application to the scattering of excited hydrogen atoms from insulator surfaces is considered.

Using a semiclassical rescattering model, the momentum distribution of recoil ions from laser-induced nonsequential double ionization is obtained and the result is consistent with the experiment reported recently. We show that the characteristic double-hump structure of the recoil momentum distribution of the ${\mathrm{He}}^{2+}$ ion parallel to the polarization axis is just the consequence of the rescattering dynamic of nonsequential double ionization and the acceleration of the ions in the laser field.

In the limit $\overrightarrow{ħ}0,$ a tunneling particle can be shown to follow classical trajectories which experience in the classically forbidden region a deep well rather than a potential barrier and, therefore, spend a very small amount of time there. Such trajectories interfere destructively. While the tunneling rate is small, the tunneling itself is very fast.

This paper contains the formalism for a new object: an “action-dependent wave function.” The peaks and valleys of this function move through space as the action is varied. For some simple action-dependent wave packets, this motion mimics the trajectories of a classical particle. Unlike time-dependent wave packets, the action-dependent wave packets do not disperse when the classical motion is separable. I will present the results for three simple cases. For one-dimensional systems and separable multidimensional systems, a large number of states can be superposed to give a sharply peaked function, which exactly tracks the classical motion.

Hoping to simplify the classification of pure entangled states of multi $\mathrm{}\left(m\right)\mathrm{}-\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{t}\mathrm{e}$ quantum systems, we study exactly and asymptotically (in $n)$ reversible transformations among $n\mathrm{th}$ tensor powers of such states (i.e., $n$ copies of the state shared among the same $m$ parties) under local quantum operations and classical communication (LOCC). For exact transformations, we show that two states whose marginal one-party entropies agree are either locally unitarily equivalent or else LOCC incomparable. In particular we show that two tripartite Greenberger-Horne-Zeilinger states are LOCC incomparable to three bipartite Einstein-Podolsky-Rosen (EPR) states symmetrically shared among the three parties. Asymptotic transformations yield a simpler classification than exact transformations; for example, they allow all pure bipartite states to be characterized by a single parameter—their partial entropy—which may be interpreted as the number of EPR pairs asymptotically interconvertible to the state in question by LOCC transformations. We show that $m-\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{t}\mathrm{e}$ pure states having an $m-\mathrm{w}\mathrm{a}\mathrm{y}$ Schmidt decomposition are similarly parametrizable, with the partial entropy across any nontrivial partition representing the number of standard quantum superposition or “cat” states $|0^{\otimes m}〉+|1^{\otimes m}〉$ asymptotically interconvertible to the state in question. For general $m-\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{t}\mathrm{e}$ states, partial entropies across different partitions need not be equal, and since partial entropies are conserved by asymptotically reversible LOCC operations, a multicomponent entanglement measure is needed, with each scalar component representing a different kind of entanglement, not asymptotically interconvertible to the other kinds. In particular we show that the $m=4\mathrm{}$ cat state is not isentropic to, and therefore not asymptotically interconvertible to, any combination of bipartite and tripartite states shared among the four parties. Thus, although the $m=4\mathrm{}$ cat state can be prepared from bipartite EPR states, the preparation process is necessarily irreversible, and remains so even asymptotically. For each number of parties $m$ we define a minimal reversible entanglement generating set (MREGS) as a set of states of minimal cardinality sufficient to generate all $m-\mathrm{p}\mathrm{a}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{t}\mathrm{e}$ pure states by asymptotically reversible LOCC transformations. Partial entropy arguments provide lower bounds on the size of the MREGS, but for $m>\mathrm{}2\mathrm{}$ we know no upper bounds. We briefly consider several generalizations of LOCC transformations, including transformations with some probability of failure, transformations with the catalytic assistance of states other than the states we are trying to transform, and asymptotic LOCC transformations supplemented by a negligible $\left[o\right(n\left)\mathrm{}\right]$ amount of quantum communication.

We show that not all four-party pure states are Greenberger-Horne-Zeilinger (GHZ) reducible (i.e., can be generated reversibly from a combination of two-, three-, and four-party maximally entangled states by local quantum operations and classical communication asymptotically). We also present some properties of the relative entropy of entanglement for those three-party pure states that are GHZ reducible, and then we relate these properties to the additivity of the relative entropy of entanglement.

Total binding energies of several charge states of cesium, including all rare-gas configurations, are calculated in the framework of relativistic many-body perturbation theory and the multiconfiguration Dirac-Fock method. We do a detailed comparison of the correlations obtained by these two methods, from which we can obtain information on the accuracy of the predictions. We thus provide benchmark calculations to assess how accurately atomic masses can be deduced from highly charged ions, for both present and future Penning-trap experiments. One-electron radiative corrections are included and the screening of the self-energy is evaluated using the Welton approximation.

We have performed an alternative resonant x-ray emission (RXE) experiment involving a transition-metal ion in the gas phase. The complex spectral behavior is explained by an Anderson impurity model taking into account bound and continuum states and Coster-Kronig transitions. Low-energy excitations corresponding to the ligand field splitting are identified. We find that spectra are quite different from recent RXE from solid-state ${\mathrm{Ti}}^{4+}$ compounds. An unexpectedly strong resonance involving Coster-Kronig transitions is explained. Good agreement between theory and experiment is obtained without inclusion of a full intermediate state multiplet calculation.

The integral and the differential photoionization cross sections of carbon dioxide are computed in the random-phase approximation coupled with a K-matrix based technique. The use of special polynomial spherical Gaussian-type orbitals provides an adequate representation of the electronic continuum. Ionization channels originating from occupied valence shell orbitals are considered, both in the separated- and interacting-channel approaches up to a photon energy of 100 eV. An accurate account of the effect of the interaction between the different excitation channels is found to be essential in order to reproduce the features observed in the experimental photoabsorption and photoionization spectra.

The recent generalized Lassettre expansion (GLE) [Phys. Rev. Lett. 81, 961 (1998)] employing only a single Regge pole is used to demonstrate the applicability of the Lassettre limit theorem over the entire electron impact energy without the involvement of the nonphysical region of the apparent generalized oscillator strength (AGOS). At forward scattering the GLE yields the unique long-sought-after normalization curve to the optical oscillator strength of the measured relative electron differential cross sections (DCS’s) through the AGOS. Optically allowed transitions in H, He, Xe, and ${\mathrm{N}}_2\mathrm{O}$ are used to illustrate the normalization procedure. We conclude that the GLE together with the momentum dispersion method of Haffad et al. [Phys. Rev. Lett 76, 2456 (1996)] now constitute a set of invaluable methods for use in guiding electron DCS measurements, including the identification of incorrectly normalized and/or spuriously behaved data in the difficult to measure small angular regime. It is hoped that this paper will inspire more measurements of DCS’s at zero-angle scattering, since currently very few such measurements are available.

We observe bound states just below the dissociation limit and shape and Feshbach resonances between the ground state hyperfine asymptotes by Raman spectroscopy on a molecular beam of sodium dimers. The rotational selectivity of a two-photon transition gives access to specific states of nuclear motion and thus to cold collision properties of two colliding atoms. Modeling of the collisional resonance structures requires a multichannel treatment of the nuclear dynamics that uses highly accurate $X{}^1{\Sigma }_g^{+}$ and $a{}^3{\Sigma }_u^{+}$ potentials. These potentials are constructed from bound levels just below the ground state asymptote measured in this experiment and bound state information available in the literature. We also present simulations of the spectrum between the ground state hyperfine asymptotes. The good agreement shows that accurate potentials obtained from bound state information are able to reproduce scattering properties of two colliding sodium atoms. From this analysis we find for the scattering lengths ${a(f=2\mathrm{})=a}_{1,-1}{=52.98\mathrm{}\left(40\right)a}_0,$ $a_{\mathrm{singlet}}{=19.20\mathrm{}\left(30\right)a}_0,$ and $a_{\mathrm{triplet}}{=62.51\mathrm{}\left(50\right)a}_0,$ where ${1a}_0=0.052\mathrm{}9177$ nm.

The Landau-Lifshitz method of calculating quasiclassical matrix elements is generalized for the case when one of the states is not quasiclassical in the JWKB sense but possesses JWKB asymptotics. The generalized Landau-Lifshitz matrix elements are expressed via the standard Landau-Lifshitz matrix elements and the suppression-enhancement amplitudes. An analytical expression for the latter quantity is presented for the Morse potential. The results obtained are used for a simple interpretation of the recent numerical data [N. Balakrishnan, R. C. Forrey, and A. Dalgarno, Phys. Rev. Lett. 80, 3224 (1998)] for the s-wave vibrational relaxation of ${\mathrm{H}}_2$ on He.

Distorted-wave calculations are carried out for the electron-impact ionization of atomic ions in the Mn isonuclear sequence. Detailed level to level calculations are performed for the dominant excitation-autoionization contributions. The validity of the configuration-average approach is studied and used to calculate direct ionization and higher n excitation-autoionization, when the level to level approach proves computationally too demanding. A combination of the two methods is used to analyze the recent crossed-beams experimental measurements of ${\mathrm{Mn}}^{5+},$ ${\mathrm{Mn}}^{6+},$ ${\mathrm{Mn}}^{7+},$ and ${\mathrm{Mn}}^{8+}$ by Rejoub and Phaneuf [Phys. Rev. A 61, 032706 (2000)]. The comparison between theory and experiment indicates that a large fraction of the initial population of each measured ion is in metastable states of excited configurations.

We have measured the absolute cross sections for the L-subshell ionization for Yb, Au, and Bi induced by intermediate and low-energy F ions. A comparative study of the different methods of extracting the vacancy production cross sections from the L x-ray line intensities is presented. The measured cross sections are compared with the available theoretical calculations based on the perturbed stationary state (PSS) approximation including the effects due to the increased binding energy, Coulomb (C) deflection, energy (E) loss, and the relativistic (R) wave function (ECPSSR). In the case of Yb and Au targets, the ratio of the subshell ionization cross section for $L_1$ to that for $L_2$ is found to be larger than 1.0 contrary to theoretical predictions, whereas the ratio is less than 1.0 for Bi, as expected. Similar ratios for the $L_2$ to $L_3$ subshells are, however, in agreement with the theoretical predictions for all three targets. These observations can be understood in terms of the multiple vacancies in the outer shells and their effect on the fluorescence yields and Coster-Kronig transitions. In the case of $L_1$ ionization, the ECPSSR calculations are found to fall much below the experimental data for Yb and Au, and a part of the deviation is understood to be due to the existence of multiple vacancies in the outer shells and the interplay between the Coster-Kronig and radiative transition probability. Quantitative estimates on the enhancement in the effective fluorescence yields of the $L_1$ subshell are also provided for all three targets.