A nuclear wave-packet description of the photodissociation of LiF is described, with emphasis on the dynamics associated with the formation of long-lived resonances. The predissociation is described using ab initio potential-energy curves and transition dipole matrix elements. The split operator method is used to propagate time-dependent coupled-channel wave functions in a diabatic representation. Dissociation is incorporated using absorbing potentials at large internuclear separations to prevent the return of flux from asymptotic regions. Extremely narrow resonances and broad window resonances are found atop a broad absorption envelope, in agreement with a recent stationary-state calculation. The lifetimes of the narrow resonances extend to hundreds of picoseconds, indicating the very slow nature of the dissociation dynamics. The features of the absorption spectrum are connected to specific aspects of the wave-packet motion on the ionic and covalent potential curves through a detailed study of the autocorrelation function.

Quantal manifestations of classical-mechanical structures (tori, invariant manifolds) are some of the least understood aspects of the Correspondence Principle. All too often, the very involved dynamics and the absence of proper tools has hampered progress, which has been driven by concrete examples. In this paper, we show the usefulness of a special “classically localized” wave packet which is designed to reveal intricate classical structures, such as homoclinic orbits, even deep in the chaotic region. Liapunov exponents can also be predicted accurately through its autocorrelation function, and even very small features of the classical dynamics can be detected and contrasted with their quantal counterparts.

We present the results of experimental and theoretical investigations into the photoionization spectra of Ba Stark states at energies resonant with the $5d7d{}^1{D}_2$ perturber level starting from the $5d6p{}^3{D}_1^o$ state. The electric field is strong enough to allow the electrons to classically escape the atom, thus transforming the perturber state into a resonance. Much of the dynamics of this remarkably complex system may be understood qualitatively. In particular, we stress the role played by electron escape time in qualitatively changing the correlation by reducing the singlet-triplet mixing and triplet excitation. A theoretical formulation of multichannel systems in static electric fields is developed which allows us to efficiently obtain both total and partial cross sections; this formulation can be used to describe the Rydberg states of atoms and molecules in static electric fields.

We study the dynamics of a magnetically trapped Bose-Einstein condensate in the presence of an external electromagnetic-field coupling trapped, untrapped, and antitrapped Zeeman sublevels. For large condensates an approximate analytical solution of the coupled Gross-Pitaevskii equations is given in the regime of strong outcoupling. The theory is developed for the cases of rf outcoupling within a hyperfine manifold of states, microwave outcoupling connecting states in two different hyperfine manifolds, and Raman outcoupling.

A homogeneous Bose gas is investigated at finite temperature using renormalization-group techniques. A nonperturbative flow equation for the effective potential is derived using sharp and smooth cutoff functions. Numerical solutions of these equations show that the system undergoes a second-order phase transition in accordance with universality arguments. We obtain the critical exponent $\nu =\mathrm{0.73.}\mathrm{}$

The validity of the shape-independent approximation is studied for three trapped atoms. By comparing the total ground-state energy calculated using pseudopotentials in the Hartree-Fock approximation to the exact ground-state energy, the shape-independent approximation is shown to agree quantitatively only in the low-density limit. It is also shown using configuration interaction that a Dirac $\delta$ function is not suitable as a replacement for the two-body interaction in exact theories.

We study the spin-mixing dynamics of an $f=1\mathrm{}$ spinor condensate. We show that the dynamics is sensitive to the relative phase and particle number distribution among the individual components of the condensate, and find that complex structures can develop in the density profiles during the time evolution. We investigate the different time scales of the spin-mixing process and their dependence on the total particle number.

We discuss a method for reconstructing the wave function of an atomic beam with the help of a self-referencing principle. At the heart of the method lies the controlled superposition of the original atomic matter wave with a single reference wave. For this purpose, Bragg scattering of atomic beams at standing light fields turns out to be perfectly suited.

An exact theory for the density of a one-dimensional Bose-Einstein condensate with hard-core particle interactions is developed in second quantization and applied to the scattering of the condensate by a spatially periodic impulse potential. The boson problem is mapped onto a system of free fermions obeying the Pauli exclusion principle to facilitate the calculation. The density exhibits a spatial focusing of the probability density as well as a periodic self-imaging in time, or Talbot effect. Furthermore, the transition from single-particle to many-body effects can be measured by observing the decay of the modulated condensate density pattern in time. The connection of these results to classical and atom optical phase gratings is made explicit.

We consider the interaction between a Bose-Einstein condensate and a single-mode quantized light field in the presence of a strong far-off-resonant pump laser. The dynamics is characterized by an exponential instability, hence the system acts as an atom-photon parametric amplifier. Triggered by a small injected probe field, or simply by quantum noise, entangled atom-photon pairs are created which exhibit nonclassical correlations similar to those seen between photons in the optical parametric amplifier. In addition, the quantum statistics of the matter and light field depend strongly on the initial state which triggers the amplifier. Thus, by preparing different initial states of the light field, one can generate matter waves in a variety of quantum states, demonstrating optical control over the quantum statistics of matter waves.

We investigate the structure and collective modes of a planar surface of a trapped Bose-Einstein condensed gas at zero temperature. In the long-wavelength limit we find a mode similar to the gravity wave on the surface of a fluid with the frequency $\omega$ and the wave number q related by ${\omega }^2=Fq/m.\mathrm{}$ Here F is the force due to the confining potential at the surface and m is the particle mass. At shorter wavelengths we use a variational approach and find corrections to ${\omega }^2$ of order $q^4\ln q.\mathrm{}$ We demonstrate the usefulness of the concept of an effective surface tension for describing both static and dynamic properties of condensed atomic clouds.

We study the stabilization of a large negative scattering length Bose-Einstein condensate by using a multisoliton fringe system. Each fringe behaves like a quasiparticle and the whole cloud forms a stable system when the trapping in one or two directions is switched off. The resulting system can be used as a coherent source of atomic solitons. A discussion on how to generate the soliton fringe system experimentally is made.

We derive an exact recursion formula for the calculation of thermodynamic functions of finite systems obeying Bose-Einstein statistics. The formula is applicable for canonical systems where the particles can be treated as noninteracting in some approximation, e.g., like Bose-Einstein condensates in magnetic traps. The numerical effort of our computation scheme grows only linearly with the number of particles. As an example, we calculate the relative ground-state fluctuations and specific heats for ideal Bose gases with a finite number of particles enclosed in containers of different shapes.

The local-field effects are considered which are feasible in a dense ensemble of resonant atoms modeled by multilevel quantum systems. Our approach is based on the generalized two-level system [V.S. Butylkin, A.E. Kaplan, and Yu.G. Khronopulo, Zh. Éksp. Teor. Fiz. 59, 921 (1970)]. Making use of this model, we take account of the nonresonant polarization and Stark shift of the absorption line due to the difference in linear polarizabilities of atoms in ground and excited states. With near dipole-dipole interaction and quadratic Stark effect included simultaneously, new features of the hysteresis behavior of the population difference as a function of the external-field intensity are predicted.

We report an interference experiment in which photon pairs generated by spontaneous parametric down-conversion produce a Young-type fourth-order interference pattern after being scattered by two different and spatially separated apertures, whose superposition defines a double slit. The experiment is compared with previous ones based on parametric down-conversion, and its nonlocal nature is discussed. A theoretical explanation is also provided.

We investigate both experimentally and theoretically the dynamics of a semiconductor laser with optical feedback in the low-frequency fluctuation regime. First we demonstrate that low-frequency fluctuations can be observed for both single and multimode operation of a semiconductor laser with optical feedback. The analysis of the fast dynamics associated with this low-frequency instability is well described by single-mode rate equations. In the multimode regime, fast pulsation is observed in every laser mode. In this case the fluctuations in total intensity are much smaller than those in the intensity of each individual mode. This indicates the presence of anticorrelations dynamics at high frequency between the different laser modes.

The two-photon spectrum of sodium atoms, excited by two counterpropagating evanescent waves, is investigated both experimentally and theoretically. Sub-Doppler linewidths are observed, which are quantitatively reproduced by a rigorous theoretical approach that takes into account optical pumping and transit time broadening due to the translational motion of the arriving and departing atoms through the evanescent-wave fields. The velocity distribution of the atoms desorbing from the surface is found to obey a cosine law, which has a significant influence on the observed line shapes.

We solve exactly the non-Markovian dynamics of a cavity mode in the presence of a feedback loop based on homodyne measurements, in the case of a nonzero feedback delay time. With an appropriate choice of the feedback parameters, this scheme is able to significantly increase the decoherence time of the cavity mode, even for delay times not much smaller than the decoherence time itself.

We study the generation of subfemtosecond pulses with the molecular coherence control in stimulated Raman scattering. We show analytically that the antiphased state temporally advances the higher frequencies with respect to the lower frequencies during a beating cycle. After some propagation distance, due to the dispersion and the difference between the antiphased and phased states in advancing high or low frequencies, the coherence is highest on the negative side of the detuning, when the two-photon Rabi frequency is about equal to the detuning. This asymmetry of the coherence magnitude with respect to the negative and positive sides of the Raman detuning is reflected in the behavior of the tuning characteristics of the high-order frequency components. When the Raman detuning is small, although the process is nonadiabatic, the subfemtosecond pulse generation may occur for both negative and positive sides of the detuning.

The beam splitter is an optical analog for spin and angular momentum. Using SU(2) group operator methods, we demonstrate how the unitary class of Robertson intelligent spin states can be generated and tested for generalized minimum uncertainty by photomixing of photon pairs from parametric down-conversion.