We analyze the dynamical stability of common spatial, or breathe-together, modes for a system of two trapped interacting Bose-Einstein condensates, when the condensates are resonantly coupled by a strong driving field. We show analytically that the dynamical stability is governed by a set of dressed atom collision parameters, and that the driving field typically destabilizes breathe-together modes which are stable in the absence of driving and vice versa. By means of numerical solutions we illustrate the consequences of this phenomenon for a number of interacting condensates consisting of pairs of ground hyperfine states of both sodium and rubidium.

A Yukawa-like equation, introduced to evaluate the first order correlation function in a Bose-Einstein condensate, can be used to evaluate the atomic density fluctuations. It does not require a few mode approximation. We apply this approach to calculate the atomic fluctuations of a condensate of attractive atoms in a double-well potential. The atomic system undergoes a spatial symmetry breaking above a critical number $N_c$ of atoms. Near $N_c$ the atomic fluctuation $\delta N$ inside a single well becomes very large and experimentally observable by a phase-contrast imaging technique. $\delta N$ is related to the collective mode temperature, which may be different from the condensate temperature measured by means of the thermal tails. A one-dimensional array of wells is also considered.

The reduced dipole matrix element for the atomic or ionic transition $|l^n\left[L_1{S}_1\right]l_1^m\left[L_2{S}_2\right]L_0{S}_0\overrightarrow{〉}|l^{n-1}\left[L_1^{\prime }{S}_1^{\prime }\right]l_1^m\left[L_2{S}_2\right]\left[L_c{S}_c\right]l_i^{\prime }\mathrm{LS}〉$ has been evaluated in the LS coupling scheme. The matrix element is particularly designed to study the process of photoionization for atoms or ions having two open subshells. The resultant expression has been checked against the standard formula in the literature by reducing it to that for the case of a single open subshell. The reduced dipole matrix element has been used to study the photoionization of chromium $4s$ and oxygen $2s$ and the asymmetry parameter β for atoms having two open subshells.

We present an application of particle statistics to the problem of optimal ambiguous discrimination of quantum states. The states to be discriminated are encoded in the internal degrees of freedom of identical particles, and we use the bunching and antibunching of the external degrees of freedom to discriminate between various internal states. We show that we can achieve the optimal single-shot discrimination probability using only the effects of particle statistics. We discuss interesting applications of our method to detecting entanglement and purifying mixed states. Our scheme can easily be implemented with the current technology.

We have employed monochromatized synchrotron radiation to measure the ${\mathrm{Be}}^{+}$ ion yield in the photon energy region of the Be $2pn\mathcal{l}(n=3\mathrm{}–12)$ double excitations. The energy positions of the resonances are in good agreement with a previous experiment [J. M. Esteva, G. Mehlman-Balloffet, and J. Romand, J. Quant. Spectrosc. Radiat. Transf. 12, 1291 (1972)] and theoretical calculations. We also report the experimentally determined Fano parameters of the widths $\Gamma$ and profile parameters q for the $2pns$ $(n<~8)$ resonances. The q values are about $-0.54$ except for $n=3\mathrm{}$ with a clearly lower value of $-0.93\left(5\right).$

We have derived cross sections for Compton scattering of very hard incident photons $\left(ħ{\omega }_1\gg {\mathrm{mc}}^2\right)$ from K-shell electrons, exact in the nuclear charge Z. The nuclear potential was taken to be of Coulomb form. The calculation of the extreme relativistic (ER) S-matrix element involved was carried out analytically. In the present case, this is the viable alternative to an impracticable ab initio numerical computation. In order to obtain the dominant behavior of the matrix element in the large ${\omega }_1$ limit, the momentum transferred to the nucleus needs to be ascribed a constant (albeit arbitrary) value in the limiting process. The result depends critically on the spectral range in which the scattered-photon energy ${\omega }_2$ $\mathrm{is}\mathrm{situated}.$ We start by considering the ${\omega }_2$ range covering the Compton line, for which the ratio ${\omega }_2/{\omega }_1$ needs to be kept finite. We show that in the ER limit the Dirac electron spinors and Green’s operator entering the S-matrix element can be replaced by their relativistically modified Schrödinger counterparts. This allows the application of integration methods developed by us earlier for the nonrelativistic matrix element. Remarkably enough, the sixfold integrals of the ER matrix element can eventually be reduced to single integrals, expressible in terms of generalized hypergeometric functions. The doubly differential cross section $d^2\sigma /d{\omega }_{2}d{\Omega }_2$ for the range of Compton line finally results as a twofold integration, requiring a simple numerical computation. This is a rather unique example of a most elaborate Coulomb problem that could be solved analytically, essentially in closed form. We subsequently consider the low- $({\omega }_2\to 0)$ and high-frequency $({\omega }_2\to {\omega }_2^{\max })$ ends of the scattered photon spectrum. For ${\omega }_2\to 0$ we find the expected infrared divergence, and verify the soft-photon theorem, which represents an important check on our calculation. Finally, we present our numerical results for $d^2\sigma /d{\omega }_{2}d{\Omega }_2,$ analyzed at fixed ${\omega }_2$ (angular distributions), or fixed photon scattering angle (spectral distributions). We discuss the “defect” and the width of the Compton line for both distributions.

Absolute cross sections for dissociative electron attachment (DEA) to ${\mathrm{NO}}_2$ have been measured and compared with that of ${\mathrm{O}}_3.$ A striking similarity is observed in the dissociation channels and the relative cross sections between the two molecules. This similarity is interpreted in terms of a common mechanism for electron capture to the two molecules and is exploited to characterize the nature of the ${\mathrm{NO}}_2$ resonances in analogy with ${\mathrm{O}}_3,$ using specific quantum chemical calculations as well as experimental data. This experimental observation and its interpretation seeks to direct attention to a previously uncommented on aspect of the DEA phenomenon in relation to molecules that are isoelectronically unrelated. The observation also tends to highlight the dominance of electronic polarizability in the electron-molecule scattering potential leading to capture.

In this work, we present a joint theoretical and experimental study on electron-${\mathrm{H}}_2\mathrm{S}$ collisions in the low- and intermediate-energy range. More specifically, we report measured elastic differential, integral, and momentum-transfer cross sections in the (100–500)-eV energy range. In addition, calculated elastic cross sections in the (0.5–500)-eV energy range are also reported. The measurements were performed using a crossed electron beam–molecular beam geometry. The angular distributions of the scattered electrons were converted to absolute cross sections using the relative flow technique. Theoretically, an optical potential is used to represent the electron-molecule interaction. The Schwinger variational method combined with the distorted-wave approximation is used to solve the scattering equations. The comparison between our calculated and measured results as well as with other available experimental and theoretical data in the literature is encouraging.

We discuss photoelectron spectra (PES) of Na and K clusters for various charge states and various sizes. The PES were obtained in dynamical calculations with time-dependent local-density approximation (TDLDA) augmented with a self-interaction correction to arrange the correct ionization properties. Comparison with experimental data shows that TDLDA provides generally a pertinent description. A few deviations for very small systems hint at final state correlations which go beyond a mean-field description.

Using techniques of ultrafast coherent control, we propose a method to produce high-purity high-$\mathcal{l}$ (angular momentum) states in Rydberg Stark wave packets. Two time-delayed phase-locked laser pulses excite the atom from a low-lying “launch state” into a low-$\mathcal{l}$ Rydberg wave packet, in the presence of a static electric field. By choosing the time delays between the pulses, and the static electric field, we find that a high-$\mathcal{l}$ state with high purity can be created at the target time.

It is shown that the translational degrees of freedom of a large variety of molecules, from light diatomic to heavy organic ones, can be cooled sympathetically and brought to rest (crystallized) in a linear Paul trap. The method relies on endowing the molecules with an appropriate positive charge, storage in a linear radio frequency trap, and sympathetic cooling. Two well-known atomic coolant species ${}^9{\mathrm{Be}}^{+}$ and ${}^{137}{\mathrm{Ba}}^{+}$ are sufficient for cooling the molecular mass range from 2 to 20 000 amu. The large molecular charge required for simultaneous trapping of heavy molecules and of the coolant ions can easily be produced using electrospray ionization. Crystallized molecular ions offer vast opportunities for novel studies.

The dynamics of a discrete soliton in an array of Bose-Einstein condensates under the action of a periodically time-modulated atomic scattering length [Feshbach-resonance management (FRM)] is investigated. The cases of both slow and rapid modulations, in comparison with the tunneling frequency, are considered. We employ a discrete variational approach for the analysis of the system. The existence of nonlinear resonances and chaos is predicted at special values of the driving frequency. Soliton splitting is observed in numerical simulations. In the case of the rapid modulation, we derive an averaged equation, which is a generalized discrete nonlinear Schrödinger equation, including higher-order effective nonlinearities and intersite nonlinear interactions. Thus the predicted discrete FRM solitons are a direct matter-wave analog of recently investigated discrete diffraction-managed optical solitons.

We experimentally study the polarization dynamics during the switch-on transient of a quasiisotropic ${\mathrm{CO}}_2$ laser emitting on the ${\mathrm{TEM}}_{01}^{*}$ mode. We observe a complex dynamics in which a spatial mode and polarization competition are involved. The observed dynamics is well reproduced by means of a model that provides a quantitative discrimination between the intrinsic asymmetry due to the kinetic coupling of molecules with different angular momenta and the residual extrinsic anisotropies due to cavity misalignments.

A stability chart of mixed ${}^4\mathrm{He}$ and ${}^3\mathrm{He}$ clusters has been obtained by means of the diffusion Monte Carlo method, using both the Aziz HFD-B and the Tang-Toennies-Yiu atom-atom interaction. The investigated clusters contain up to eight ${}^4\mathrm{He}$ atoms and up to 20 ${}^3\mathrm{He}$ atoms. One single ${}^4\mathrm{He}$ binds 20 ${}^3\mathrm{He}$ atoms, and two ${}^4\mathrm{He}$ bind 1, 2, 8, and more than 14 ${}^3\mathrm{He}$ atoms. All clusters with three or more ${}^4\mathrm{He}$ atoms are bound, although the combinations ${}^4{\mathrm{He}}_3^3{\mathrm{He}}_{9,10,11}$ and ${}^4{\mathrm{He}}_4^3{\mathrm{He}}_9$ are metastable. Clusters with 2, 8, and 20 ${}^3\mathrm{He}$ atoms are particularly stable and define magic ${}^3\mathrm{He}$ numbers.

Ab initio calculations of cross sections and rate constants for elastic scattering and Zeeman relaxation in collisions of $\mathrm{NH}\left(X{}^3{\Sigma }^{-}\right)$ molecules with ${}^3\mathrm{He}$ atoms in a magnetic field are presented and the mechanism for Zeeman transitions in ground-state ${}^3\Sigma$ molecules is established. The potential surface for He-NH interaction is obtained using all-electron coupled-cluster calculations with single, double, and noniterative triple excitations in a basis set augmented by bond functions. The ratio of the rates for elastic energy transfer and Zeeman relaxation in NH-${}^3\mathrm{He}$ collisions exceeds ${10}^5$ at temperatures between $0.5$ and 1 K.

Similarities between alkali-metal gases in optical lattices with noninteger occupation of the lattice sites and quantum crystals are explored. The analogy with the vacancy liquid (VL) provides an alternative explanation to the Mott transition for the recent experiment on the phase transition in the lattice. The VL can undergo Bose-Einstein condensation (BEC) with $T_c$ within experimental reach. Direct and vacancy-assisted mechanisms of the band motion for hyperfine impurities are discussed. A large concentration of vacancies can result in the spatial decomposition of the system into pure hyperfine components. Below the vacancy condensation the impurity component resembles ${}^3\mathrm{He}$ in ${}^3\mathrm{He}–\mathrm{He}$ II mixtures.

A demonstration of a transient collisional x-ray laser pumped by only a single profiled picosecond laser pulse is reported. Saturated operation on the $4d-4p$ transition in Ni-like silver at 13.9 nm is demonstrated using a pump energy of less than 3 J, i.e., more than halved in comparison to the best achievements in the double-pulse scheme. The pump laser pulse characteristics, traveling excitation wave, and x-ray output are discussed as well.

The strong subadditivity inequality for a three-particle composite system is an important inequality in quantum information theory which can be studied via a four-particle entangled state. We use two three-level atoms in $\Lambda$ configuration interacting with a two-mode cavity and the Raman adiabatic passage technique for the production of the four-particle entangled state. Using this four-particle entanglement, we study various aspects of the strong subadditivity inequality.

We calculate spectra and wave functions of Rydberg atoms in strong magnetic fields using adiabatic basis sets, which reflect the different time scales of the electronic motion parallel and transverse to the magnetic field. For large absolute values of the azimuthal quantum number m, nonadiabatic corrections are found to be negligible, and the adiabatic basis states and their energies are exact solutions. With decreasing value of $|m|,$ the system turns nonadiabatic, and the statistical behavior of the spectra changes from being consistent with classically regular to being consistent with classically chaotic motion. A relation describing the parameter region in which this transition occurs is obtained.

We report an efficient trapping of rare-earth-metal Yb atoms with a high-power violet laser diode (LD). An injection-locked violet LD with a 25-mW frequency-stabilized output was used for the magneto-optical trapping (MOT) of fermionic as well as bosonic Yb isotopes. A typical number of $4\times {10}^6$ atoms for ${}^{174}\mathrm{Yb}$ with a trap density of $\sim 1\times {10}^8{\mathrm{cm}}^{-3}$ was obtained. A 10-mW violet external-cavity LD was used for the one-dimensional slowing of an effusive Yb atomic beam without a Zeeman slower resulting in a 35-fold increase in the number of trapped atoms. The overall characteristics of our compact violet MOT, e.g., the loss time of 1 s, the loading time of 400 ms, and the cloud temperature of 0.7 mK, are comparable to those in previously reported violet Yb MOTs, yet with a greatly reduced cost and complexity of the experiment.