The breakup of ${\mathrm{D}}_2$ following the absorption of a single photon, leading to four free charged particles interacting via the Coulomb force, has been investigated. Triply differential cross sections (TDCSs) of the two ejected electrons were measured for selected asymmetric kinematic conditions, namely, a 20 eV electron in coincidence with a 5 eV “reference” electron fixed at four different angles. The results are compared with helium TDCSs and, although the respective angular distributions have similar features, there are surprising differences that could have their origin in two-center interference effects.

A theory is presented for the calculation of molecular inner-shell photoionization near thresholds and electron–molecular-ion elastic scattering. The interaction of the incoming/outgoing electron with each atom of the formation (except for the ionized atom) is accounted for by suitable boundary conditions imposed on the electron wave function at nuclei of these atoms in the system. The theory is applied to calculations of the form of the photoelectron angular distribution for $1s$ photoionization of the C atom in the CO diatomic molecule, as well as for the photoelectron angular distribution due to photodetachment from a quasimolecular negative ion consisting of a ${\mathrm{C}}^{-}$ ion located near a neutral O atom.

Light-induced drift of optically active atoms in a buffer gas is a consequence of the unequal diffusive frictions suffered by the excited and the ground-state atoms. This drift can be used to create an “optical piston,” in which the active atoms are pushed forward by light through the semipermeable membrane of the buffer gas. Normally, optical piston effect is studied when the active atoms are neutral in a confined one-dimensional situation. We present a detailed theory of this phenomenon when the active atoms are charged and a magnetic field is applied for “tuning” the direction as well as the magnitude of the drift, thus removing the necessity of confinement. Our study is in different geometries of the light beam and the magnetic field, first in the weak collision model, and then for the strong collision and the Boltzmann-Lorentz models.

We present a time-dependent density-functional theory (TDDFT) with proper asymptotic long-range potential for nonperturbative treatment of multiphoton processes of many-electron molecular systems in intense laser fields. A time-dependent generalized pseudospectral method is extended for precision solution of the TDDFT equations for two-center diatomic systems. The procedure allows nonuniform optimal spatial grid discretization of the Hamiltonian in prolate spheroidal coordinates and a split-operator scheme in energy representation is used for the time propagation of the individual molecular spin orbital in space and time. The theory is applied to the first detailed all-electron study of multiphoton ionization and high-order harmonic generation (HHG) processes of ${\mathrm{N}}_2$ in intense laser fields. The results reveal unexpected and intriguing nonlinear optical response behaviors of the individual valence spin orbital to strong fields. In particular, it is found that the dominant contribution to the total HHG power spectrum of ${\mathrm{N}}_2$ is due to the constructive and destructive interferences of the induced dipoles of the two highest-occupied bonding $\left(3\mathrm{}{\sigma }_g\right)$ and antibonding $\left(2\mathrm{}{\sigma }_u\right)$ molecular orbitals in the presence of intense laser fields.

The effect of a driving field on the cyclotron mode of a relativistic electron in a Penning trap is studied analytically. The Hamiltonian dynamics of this driven nonlinear oscillator is analyzed by using linearization techniques and displaced squeezed-state formalism. With the approximate analytical expressions obtained for the eigenstates in this approach, a simplified treatment of the dissipative dynamics is carried out and some of the nontrivial features found in a recent numerical study [D. Enzer and G. Gabrielse, Phys. Rev. Lett. 78, 1211 (1997)] are unraveled. The emergence of different time scales and the generation of a metastable statistical mixture are understood in terms of the changes induced in the structure of the master equation by the nonuniform characteristics of the eigenstates; the partial revivals of specific coherent states are accounted for by the evolution of particular coherences. The control of these effects by a proper choice of the driving parameters is discussed.

We discuss various aspects of the single vortex state of a dilute superfluid atomic Fermi gas at $T=0.\mathrm{}$ The energy of the vortex in a trapped gas is calculated and we provide an expression for the thermodynamic critical rotation frequency of the trap for its formation. Furthermore, we propose a method to detect the presence of a vortex by calculating the effect of its associated velocity field on the collective mode spectrum of the gas.

We propose a configuration of a magnetic microtrap that can be used as an interferometer for three-dimensionally trapped atoms. The interferometer is realized via a dynamic splitting potential that transforms from a single well into two separate wells and back. The ports of the interferometer are neighboring vibrational states in the single-well potential. We present a one-dimensional model of this interferometer and compute the probability of unwanted vibrational excitations for a realistic magnetic potential. We optimize the speed of the splitting process in order to suppress these excitations, and conclude that such interferometer device should be feasible with currently available microtrap technique.

A dense vortex lattice in a rotating dilute Bose-Einstein condensate is studied with the Thomas-Fermi approximation. The upper critical angular velocity ${\Omega }_{c2\mathrm{}}$ occurs when the intervortex separation b becomes comparable with the vortex-core radius $\xi .$ For a radial harmonic trap, the loss of confinement as $\overrightarrow{\Omega }{\omega }_{\perp }$ implies a singular behavior. In contrast, an additional radial quartic potential provides a simple model for which ${\Omega }_{c2\mathrm{}}$ is readily determined. Unlike the case of a type-II superconductor at fixed temperature, the onset of ${\Omega }_{c2\mathrm{}}$ arises not only from decreasing b but also from increasing $\xi$ caused by the vanishing of the chemical potential as $\overrightarrow{\Omega }{\Omega }_{c2\mathrm{}}.$

We explore theoretically the signal generated by a fluctuating radiation field via a four-wave mixing process in an atomic vapor undergoing Markovian dephasing collisions. We consider specifically a broadband laser field well detuned from the atomic resonance and calculate the signal generated using counterpropagating pump fields as a function of the time delay of the incident probe field. We assume that the pulse duration is long compared to the correlation time of the incident fields. By considering the various time-ordered pathways and treating the incident-field amplitudes as random Gaussian variables, we find that the signal generated is dominated by two specific pathways that depend only on the incident-field bandwidth and the decay rate of the ground to excited state coherence. An interesting aspect of the far-impact-detuning case is that the signal is dominated by resonances involving spatially separated atoms. Our formalism provides a basis for describing the effects of mode correlations on four-wave-mixing signals generated by stochastic fields.

We experimentally investigate pattern formation in a solid-state microchip laser with a large Fresnel number. Controlling the reflectivity of the output coupler can generate the stable square pattern of optical vortex lattices. The formation of square vortex lattices is found to be a spontaneous process of transverse mode locking within almost-degenerated mode families. The frequency of self-induced oscillation in square vortex lattices agrees well with the numerical calculation. The chaotic relaxation oscillation is found in square vortex lattices due to the multi-longitudinal-mode operation.

This paper presents a detailed experimental study of random lasers with resonant feedback. The dependences of the lasing threshold and the number of lasing modes on the transport mean free path, the pump area, and the sample size are measured. An analytical model based on the concept of quasistates is developed to explain the behaviors of random lasers.

Many-body calculation of nuclear spin-dependent parity-nonconserving amplitude for $7s,F=\overrightarrow{4}7s,F=5$ transition between hyperfine sublevels of the ground state of ${}^{211}\mathrm{Fr}$ is carried out. The final result is $〈7s,F=5||d_{\mathrm{PNC}}||7s,F=4〉=-0.49\times {10}^{-10}i\kappa \hspace{0.5em}\mathrm{a}.\mathrm{u}.\mathrm{},$ where $\kappa$ is the dimensionless coupling constant. This is approximately an order of magnitude larger than similar amplitude in Cs. The dominant contribution to $\kappa$ is associated with the anapole moment of the nucleus.

We formulate a conclusive teleportation protocol for a system in d-dimensional Hilbert space utilizing the positive operator-valued measurement. The conclusive teleportation protocol ensures some perfect teleportation events when the channel is only partially entangled, at the expense of lowering the overall average fidelity. We discuss how much information remains in the inconclusive parts of the teleportation.

The aim of this paper is to study the peculiarities arising in a finite-basis-set implementation of the subspace density-functional theory (SDFT) for the excited states of molecules. The accuracy of different basis-set calculations is discussed within the framework of the local-density approximation. Small basis sets with adjustable parameters, optimized for each subspace energy, were found to provide a balanced description of states. On the contrary, basis sets adjusted to the ground state yield a poor approximation for the excited states. For the molecules under consideration $({\mathrm{H}}_2,$ HeH, and LiH), the SDFT accuracy for excited states compares well with ground-state density-functional theory calculations. Despite the limited basis set used the excitation energies calculated are in agreement with the more accurate ones obtained within the wave-function formalism by the configuration interaction methods.

This work combines the usual empirical formula for the effective charge of a beam penetrating a target with the Bohr charge equilibrium condition. The result is a logarithmic scaling law, which provides the rms valence velocity and virialized ionization potential for any atomic species Z at any charge state $0<~Q<Z.\mathrm{}$ Comparisons with Thomas-Fermi modeling and the Bohr formula for hydrogenic valence velocities are performed.

The maximal population transfer in three-level $\Lambda$ system driven by linear polarized few-cycle laser pulses is investigated numerically. A time-dependent Schrödinger equation without the rotating wave approximation is solved. The maximal population transfer depends critically on the chirp rate and the intensity of the pulses. Almost complete population transfer can be achieved if the difference between the transition dipole moments is not very large.

A family of equations that combines contracted Schrödinger equations of different orders is reported here. Attention is focussed on the resulting second order, third order, and fourth order of these modified-contracted Schrödinger equations. Some of these equations are self-contained and have as fixed points those corresponding to the full-configuration interaction eigenstates. The indeterminacy, which hindered initially the use of the contracted Schrödinger equations, does not formally exist in these equations. Relations linking the lower-order reduced density matrices with the higher-order matrices are exactly incorporated into the modified-contracted Schrödinger-equations structure. The cancellation of high-order correlation terms, which is hidden in the contracted Schrödinger equations, now takes an explicit form.

Coulomb blockade effects in capacitively coupled quantum dots can be utilized for constructing an N-qubit system with antiferromagnetic Ising interactions. Starting from the tunneling Hamiltonian, we theoretically show that the Hamiltonian for a weakly coupled quantum-dot array is reduced to that for nuclear-magnetic-resonance (NMR) spectroscopy. Quantum operations are carried out by applying only electrical pulse sequences. Thus various error-correction methods developed in NMR spectroscopy and NMR quantum computers are applicable without using magnetic fields. A possible measurement scheme in an N-qubit system is quantitatively discussed.

The finite-size scaling method is used to calculate the critical parameters of a two-parameter model Hamiltonian that exhibit resonances. We show the existence of a crossover phenomenon for the energy spectrum; the transition from a bound state to a continuum is a “second-order phase transition” in one region and a “first-order phase transition” in another region. As the parameters varied, the numerical value of the critical exponent of the energy levels changed from two to one. In the zone where the critical exponent equals one, the system has narrow resonances and they disappear when the exponent is two. The method has potential applicability in predicting stable and metastable atomic and molecular states. We also show that finite-size scaling methods are capable of detecting multicritical points.

We have investigated the temperature-dependent Casimir-Polder interaction between two oscillators in the proximity of metal surfaces. The interaction near a single metal surface has much in common with the interaction in free space. However, at any finite temperature the long-range asymptote is equal to the high-temperature asymptote. This asymptote, which originates not from the $n=0\mathrm{}$ term in the Matsubara summation but from thermal population of the $n>\mathrm{}0\mathrm{}$ terms, is $F\left(R\right)=-{2k}_{B}T{\alpha }_0^2{/R}^6.$ This should be compared with the more rapidly decaying zero-temperature Casimir-Polder asymptote, $F\left(R\right)\mathrm{}\approx -13ħc{\alpha }_0^2/\left(2\mathrm{}\pi R^7\right).\mathrm{}$ The interaction in the midplane between two metallic surfaces is very different. The nonretarded interaction decreases exponentially and the interaction is dominated by an enhanced Casimir-Polder-like asymptote. At large separations this asymptote also decays exponentially. For any relevant temperatures the long-range asymptote is no longer equal to the high-temperature limit. In other words crossover to a classical limit found for the long-range interaction in free space, and on a metal surface, is not always valid in a narrow cavity.