We consider the properties of an atom laser produced by the output coupling of a trapped vortex state with a Raman scattering process. We find a linearized analytic solution from which a generalized resonance condition for Raman output coupling is developed. Using numerical simulations of a two-component Gross-Pitaevskii equation in two and three dimensions, the output beam from a trapped central vortex state is analyzed for cases of pulsed and continuous coupling where the vortex core is either transverse or parallel to the direction of propagation. We show how the parameters of the Raman light fields control the spatial phase of the output beam.

We study the time evolution of the entangled kaon system by considering the Liouville–von Neumann equation with an additional term which allows for decoherence. We choose, as generators of decoherence, the projectors to the two-particle eigenstates of the Hamiltonian. Then we compare this model with the data of the CPLEAR experiment and find in this way an upper bound on strength $\lambda$ of the decoherence. We also relate $\lambda$ to an effective decoherence parameter $\zeta$ considered previously in literature. Finally we discuss our model in the light of different measures of entanglement, i.e., von Neumann entropy S, entanglement of formation E, and concurrence C, and we relate decoherence parameter $\zeta$ to the loss of entanglement: $1-E.\mathrm{}$

Results for $K\alpha$ x-ray emission from highly charged iron ions, which were obtained from a detailed and systematic spectral model, are presented in the wavelength range from 1.84 to 1.94 Å. Account has been taken of the fundamental atomic radiative-emission processes associated with inner-shell electron collisional excitation, inner-shell electron collisional ionization, as well as dielectronic recombination. Particular emphasis has been directed at the identification of spectral features that can serve as diagnostics of extreme nonequilibrium or transient-ionization conditions, which can occur in stellar flares and supernova remnants, as well as in tokamak plasmas. In order to investigate the fundamental $K\alpha$ line-formation processes that can play a dominant role under these conditions, theoretical predictions have been compared with spectral observations of the EBIT-II x-ray emission from highly charged Fe ions in the electron-beam ion trap at the Lawrence Livermore National Laboratory. The observed spectroscopic features are found to be well represented by our theoretical calculations, validating earlier theoretical work on transient-ionization phenomena. We have identified spectral features that can serve as diagnostics of the electron density, the line-formation mechanism, and the charge-state distribution.

Dielectronic recombination (DR) from a continuum of finite bandwidth in Ba atoms has been studied in electric fields of 0–5 V/cm and magnetic fields of 0–240 G for both $\overrightarrow{B}\parallel \overrightarrow{E}$ and $\overrightarrow{B}\perp \overrightarrow{E}.$ In electric fields of ⩾0.1 V/cm, the presence of a perpendicular magnetic field increases the integrated DR rate by up to 60%, with the peak enhancement moving towards higher magnetic fields as the electric field is increased. The general behavior of the enhancement for $\overrightarrow{B}\perp \overrightarrow{E}$—as well its absence for $\overrightarrow{B}\parallel \overrightarrow{E}$ is in agreement with theoretical expectations. A simple model is presented to provide insight into the results, and reasons for its shortcomings are presented.

We discuss the quantum phases and their diffusion dynamics in a spinor-1 atomic Bose-Einstein condensate. For ferromagnetic interactions, we obtain the exact ground-state distribution of the phases associated with the total atom number $\mathrm{}\left(N\right),$ the total magnetization $\left(\mathcal{M}\right),$ and the alignment (or hypercharge) (Y) of the system. The mean-field ground state is stable against fluctuations of atom numbers in each of the spin components, and the phases associated with the order parameter for each spin components diffuse while dynamically recovering the two broken continuous symmetries [U(1) and SO(2)] when N and $\mathcal{M}$ are conserved, as in current experiments. We discuss the implications to the quantum dynamics due to an external (homogeneous) magnetic field. We also comment on the case of a spinor-1 condensate with antiferromagnetic interactions.

We study the phenomena at the overlap of quantum chaos and nonclassical statistics for the time-dependent model of nonlinear oscillator. It is shown in the framework of Mandel Q parameter and Wigner function that the statistics of oscillatory excitation numbers is drastically changed in the order-to-chaos transition. The essential improvement of sub-Poissonian statistics in comparison with an analogous one for the standard model of driven anharmonic oscillator is observed for the regular operational regime. It is shown that in the chaotic regime, the system exhibits the range of sub-Poissonian and super-Poissonian statistics which alternate one to other depending on time intervals. Unusual dependence of the variance of oscillatory number on the external noise level for the chaotic dynamics is observed. The scaling invariance of the quantum statistics is demonstrated and its relation to dissipation and decoherence is studied.

We investigate the role of spin-orbit interaction in the production of spin-polarized photoelectrons under the influence of a dressing laser. Although the scheme considered here is essentially based on the laser-induced continuum structure, it turns out that special care has to be taken for the spin states in the continua. This is because the spin-orbit interaction in the continuum cannot be neglected for our specific case. After the derivation of the general formula, specific theoretical results are presented for Rb and Cs atoms. Enhancement about a factor of 2 in the degree of spin polarization has been predicted for both systems by the introduction of a dressing laser.

We study the normal modes and the stability of two component condensates in a phase separated regime. In such a regime, the system can undergo a quantum phase-transition upon the change of interaction strength between bosons of the same species or the variation of the trap frequencies. In this transition, the distribution of the two components changes from a symmetric to an asymmetric shape. We discuss the nature of the phase transition, the role of the interface tension, and the phase diagram. The symmetric to asymmetric transition is the simplest quantum phase transition that one can imagine. We found new branches of normal modes which are specific for trapped multicomponent condensates and are analogous to the waves at the interface between two layers of immiscible fluids under gravity. At the point of the phase transition, the frequencies of those modes go to 0 and become imaginary which causes an instability. The interface tension shifts the normal-mode frequencies and changes the stability region of the system.

We consider the propagation of two laser pulses in a medium of three-level $\Lambda$ atoms with nonvanishing two-photon detuning and different oscillator strengths of the transitions. We show that the two-photon detuning and the derivative of the mixing angle are described by one and the same equation. We analyze the solution of this equation and its physical consequences. In particular, we obtain the conditions and the distance where the nonadiabaticity and the two-photon detuning may be reduced. We derive a simple expression for the maximum length to which excitation in the medium may reach.

The dynamics of classical and quantum systems, which are driven by a high-frequency $\left(\omega \right)$ field, is investigated. For classical systems, the motion is separated into a slow part and a fast part. The motion for the slow part is computed perturbatively in powers of ${\omega }^{-1}$ to the order ${\omega }^{-4},$ and the corresponding time independent Hamiltonian is calculated. Such an effective Hamiltonian for the corresponding quantum problem is computed to the order ${\omega }^{-4}$ in a high-frequency expansion. Its spectrum is the quasienergy spectrum of the time dependent quantum system. The classical limit of this effective Hamiltonian is the classical effective time independent Hamiltonian. It is demonstrated that this effective Hamiltonian gives the exact quasienergies and quasienergy states of some simple examples, as well as the lowest resonance of a nontrivial model for an atom trap. The theory that is developed in this paper is useful for the analysis of atomic motion in atom traps of various shapes.

We study a diffusive, multistable optical system with nonlocal nonlinearity where the transverse dispersion relations of traveling waves emerging from uniform states are modified by filtering the spatial frequencies. We investigate how the spatial cutoff frequency has strong effects on the position and nature of the primary bifurcation leading to traveling waves and enable the observation of secondary bifurcations of the traveling waves to a great variety of blinking and traveling bright droplets. We give an overview of the properties of waves and droplets.

Macroscopic field quantization is presented for a nondispersive photonic dielectric environment, both in the absence and presence of guest atoms. Starting with a minimal-coupling Lagrangian, a careful look at functional derivatives shows how to obtain Maxwell’s equations before and after choosing a suitable gauge. A Hamiltonian is derived with a multipolar interaction between the guest atoms and the electromagnetic field. Canonical variables and fields are determined and in particular, the field canonically conjugate to the vector potential is identified by functional differentiation as minus the full displacement field. An important result is that inside the dielectric a dipole couples to a field that is neither the (transverse) electric nor the macroscopic displacement field. The dielectric function is different from the bulk dielectric function at the position of the dipole, so that local-field effects must be taken into account.

In a recent paper, Klews and Schweizer [Phys. Rev. A 64, 053403 (2001)] presented a computational method for the three-dimensional propagation of wave packets in the hydrogen atom driven by a train of short unidirectional electric-field pulses. They argued that their computational scheme is valid for an arbitrary value of the pulse strength. We show, however, that such a scheme leads to both mathematical and physical inconsistences when strong pulses are considered, and, consequently, its validity is limited to the case of weak fields. The generalization to the case of an arbitrary pulse strength is also commented.

Recent experiments have demonstrated the spontaneous evolution of a gas of ultracold Rydberg atoms into an expanding ultracold plasma, as well as the reverse process of plasma recombination into highly excited atomic states. Treating the evolution of the plasma on the basis of kinetic equations, while ionization/excitation and recombination are incorporated using rate equations, we have investigated theoretically the Rydberg-to-plasma transition. Including the influence of spatial correlations on the plasma dynamics in an approximate way, we find that ionic correlations change the results quantitatively but not qualitatively.

We report experimental evidence of Sisyphus cooling in atoms with a ${}^1{S}_0$ ground state. Since $J=0,$ any cooling mechanism which requires multiple sublevels can only occur in the isotopes which have nuclear spin $I\ne 0.$ Ytterbium has seven stable isotopes and offers a unique system in which we can study cooling on $F=\overrightarrow{0}1$ ${(}^{168,170,172,174,176}\mathrm{Yb}),$ $F=1/\overrightarrow{2}3/2$ ${(}^{171}\mathrm{Yb}),$ and $F=5/\overrightarrow{2}7/2$ ${(}^{173}\mathrm{Yb}),$ depending on the selection of isotope. We have trapped each of the seven stable isotopes of ytterbium in a magneto-optical trap (MOT) using the strong ${}^1{S}_0{-}^1{P}_1$ transition, and transferred them into a second MOT which uses the much narrower ${}^1{S}_0{-}^3{P}_1$ intercombination transition. We have measured the temperature of isotopes ${}^{171}\mathrm{Yb},$ ${}^{173}\mathrm{Yb},$ and ${}^{174}\mathrm{Yb}$ in the ${}^1{S}_0{-}^3{P}_1$ MOT, as a function of the intensity and detuning of the trapping laser. The temperature of ${}^{174}\mathrm{Yb}$ was found to increase more rapidly with intensity than predicted by Doppler cooling theory, in agreement with earlier work on alkaline-earth atoms. In the odd isotopes the temperature was found to decrease with increasing angular momentum, as observed in earlier experiments and three-dimensional simulations.

We consider the multichannel inverse scattering problem in one dimension in the presence of thresholds and bound states for a potential of finite support. Utilizing the Levin representation, we derive the general Marchenko integral equation for N-coupled channels and show that, unlike the case of the radial inverse scattering problem, the information on the bound-state energies and asymptotic normalization constants can be inferred from the reflection coefficient matrix alone. Thus, given this matrix, the Marchenko inverse scattering procedure can provide us with a unique multichannel potential. The relationship with supersymmetric partner potentials as well as possible applications are discussed. The integral equation has been implemented numerically and has been applied to several schematic examples showing the characteristic features of multichannel systems. A possible application of the formalism to technological problems is briefly discussed.

An approach is described by which the Bethe theory for the stopping power of heavy-element targets is extended to treat the projectile in a fully relativistic way. The target electrons are treated semirelativistically by use of a modified Foldy-Wouthuysen transformation, also known as the Douglas-Kroll transformation. This approach allows results to be obtained that are valid to all orders in $v^2{/c}^2,$ with $v$ being the initial speed of the projectile. The contributions from both the longitudinal and transverse parts of the differential cross section are included, yielding a full expression for the stopping power of these systems. Our results show that the relativistic nature of the electrons in heavy-element targets leads to significant corrections which can be greater than 3% of Bethe’s original results.

We have investigated the electron capture into large-$l$ Rydberg states of multiply charged ionic projectiles (e.g., the core charges $Z=6,$ 7, and 8) escaping solid surfaces with intermediate velocities $(v\approx 1\mathrm{a}.\mathrm{u}.\mathrm{})$ in the normal emergence geometry. A model of the nonresonant electron capture from the solid conduction band into the moving large angular-momentum Rydberg states of the ions is developed through a generalization of our results obtained previously for the low-$l$ cases $(l=0,$ 1, and 2). The model is based on the two-wave-function dynamics of the Demkov-Ostrovskii type. The electron exchange process is described by a mixed flux through a moving plane (“Firsov plane”), placed between the solid surface and the ionic projectile. Due to low eccentricities of the large-$l$ Rydberg systems, the mixed flux must be evaluated through the whole Firsov plane. It is for this purpose that a suitable asymptotic method is developed. For intermediate ionic velocities and for all relevant values of the principal quantum number $n\approx Z,$ the population probability $P_{\mathrm{nl}}$ is obtained as a nonlinear l distribution. The theoretical predictions concerning the ions S VI, Cl VII, and Ar VIII are compared with the available results of the beam-foil experiments.

We report on the systematic observation of emission spectra of ${\mathrm{Rb}}^{*}{\mathrm{He}}_n$ exciplexes $(n=1,2,\dots ,6),$ realized by exciting Rb atoms to the $5^{2}P$ states $\left({\mathrm{Rb}}^{*}\right)$ in a cold ${}^4\mathrm{He}$ gas. The observed broad spectral components are assigned to ${\mathrm{Rb}}^{*}{\mathrm{He}}_n$ $(n=1\mathrm{}–6)$ using theoretical spectra obtained from ab initio potential curves. The dynamics of the exciplex formation is discussed, based on the observed temperature dependence of the spectra. The He gas density dependence of the spectra of ${\mathrm{Rb}}^{*}\mathrm{He}$ is understood as a change in the population distribution over the vibrational levels. The present results are compared with our previous work with Cs [K. Enomoto et al., Phys. Rev. A 66, 042505 (2002)], and differences are explained in terms of the difference in the fine-structure splitting. Furthermore, we show the emission spectrum observed after the excitation of Rb in liquid He and conclude that it is the fluorescence from the exciplex ${\mathrm{Rb}}^{*}{\mathrm{He}}_6.$