Measurements of the $3\overrightarrow{d}2p$ resonance and intercombination lines were made on the PLT tokamak for the neonlike ions Fe XVII, Ge XXIII, and Se XXV at several electron temperatures. The observed ratios agree with measurements of the ratios of the electron-impact excitation cross sections measured at the Livermore EBIT-II electron beam ion trap indicating that the effects of indirect excitation processes active in a plasma environment are minor for this line pair. However, the measured ratios are significantly smaller than theoretical predictions of their relative oscillator strengths or electron-impact excitation rates, illustrating the need to use laboratory measurements to calibrate this line pair at the level necessary for spectral diagnostics.

Calculations are carried out on the photoionization of ${\mathrm{C}}_{60}$ molecules in the gas phase, in particular, the photoionization of its highest occupied molecular orbital leading to the formation of ${\mathrm{C}}_{60}^{+}$ in the ${}^2{H}_u$ state. The computational treatment employs the undistorted orbitals of the neutral molecule and solves the coupled scattering equations for the ejected electron in the field of the molecular ion by using the correct static-exchange interaction within a polyatomic Schwinger variational method with Padé corrections. The total cross section and photoelectron angular distributions show marked resonant features from the threshold up to photon energy of about 30 eV. In the present calculations, all resonances are one-electron resonances of the outgoing electron and are very reminiscent of those predicted for electron-scattering processes from neutral ${\mathrm{C}}_{60}.$ The physical implications of this result are analyzed and discussed.

The influence of crossed electric and magnetic fields on dielectronic recombination of ${\mathrm{Ne}}^{7+}$ ions has been measured at the Stockholm heavy-ion storage ring CRYRING. The electron energy range covered all dielectronic recombination resonances attached to $2\overrightarrow{s}{2p}_{1/2}$ and $2\overrightarrow{s}{2p}_{3/2}$ $\Delta n=0\mathrm{}$ core excitations. Two sets of measurements at magnetic fields of 180 mT and 30 mT have been performed. For the measurement at 180 mT we applied 25 different electric fields between 0 and 1400 V/cm. The resonance strength for dielectronic recombination via high Rydberg states initially increases linearly with electric field and later levels out. At a magnetic field of 30 mT we applied 15 different electric fields ranging from 0 to 140 V/cm. Compared to the measurement at 180 mT the initial slope of the rate enhancement was larger by almost a factor of 2. The fraction of resonant strength not measured due to field ionization is estimated by a model calculation of dielectronic recombination cross sections.

We have measured cross sections for the electron-impact excitation out of the metastable levels of neon into the ten levels of the ${2p}^{5}3p$ configuration. Two sources of metastable neon atoms were used, a hollow-cathode discharge and a fast beam formed via near-resonant charge exchange. Both sources produce a mixed target of Ne in both ${(}^3{P}_0$ and ${}^3{P}_2)$ metastable levels. For the ${2p}^{5}3p$ excited levels with $J=2\mathrm{}$ or $J=3,$ the excitation is dominated by excitation from the ${}^3{P}_2$ level, and we present cross sections over the energy range of 0 to 450 eV. The results are compared with the cross sections for excitation out of the metastable levels of argon and the applications to diagnostics of ionized gas systems are discussed.

The dynamics of harmonic generation by a molecule of discrete rotational symmetry oriented in the polarization plane of a circularly polarized laser field is discussed. A simple model system is presented and the corresponding high-order harmonic generation spectrum is calculated analytically as a sum of the bound-bound and the bound-continuum contributions. It is shown that, contrary to the case of rare gas atoms interacting with linearly polarized radiation, the dominant contribution to high-order harmonic generation by the studied class of systems comes from the bound-bound transitions. As a consequence, the mechanism of the process is different from the well-known rescattering mechanism due to Corkum and Kulander. At intensities high enough the molecular harmonic generation spectra reproduce the main features of the atomic ones, i.e., the plateau and the cutoff. Unlike the cutoff in the atomic case, the molecular cutoff position depends linearly on the electric field strength and the molecular dimensions. This should allow one to reach higher harmonic orders by employing larger molecular targets.

We study the coupled translational and internal dynamics of a two-level atom in a spatially periodic optical potential created by a single-mode field in a high-finesse Fabry-Perot cavity. The strongly coupled atom-cavity system with atomic center-of-mass motion included is modeled by semiclassical nonlinear Heisenberg equations of motion with two degrees of freedom. At exact resonance between the internal atomic transition and the cavity eigenfrequency, the internal and translational degrees of freedom are separated from each other resulting in periodically modulated Rabi oscillations and regular translational motion. Near the atom-field resonance, the coupled dynamics is found to be irregular and even chaotic in the sense of extremal sensitivity to initial conditions. It is manifested as a chaotic motion of an atom in an absolutely regular spatially periodic potential in the absence of any random fluctuations. This effect may be explained as a result of the interaction of nonlinear resonances in the atom-field nonlinear pendulum whose low-frequency translational motion is modulated by the high-frequency Rabi oscillations. The irregular motion is studied in detail in numerical experiments using the arsenal of methods of the dynamical systems theory. The results obtained are compared with recent experiments with ultracold single atoms interacting with single photons in the strong-coupling regime. We estimate the ranges of the system’s control parameters, the detuning, the recoil frequency, and the mean number of intracavity photons, in which the interaction of nonlinear resonances may lead, under realistic conditions, to local instability of the center-of-mass motion and some manifestations of dynamical chaos, which is the effect of interest in studying the quantum-classical correspondence and quantum chaos in atomic optics.

A microwave analog of the interference Hanle effect has been studied in sodium Rydberg atoms. Spontaneous emission of the microwave transition ${37P}_{3/2}\to {37S}_{1/2}$ at 70.166 GHz was replaced by an induced transition from a pulsed microwave source. A dependence of population of the ${37S}_{1/2}$ state on the magnetic field was recorded in various conditions. Good agreement with the theoretical calculations has been found. The widths and shapes of observed resonances were defined by the spectral widths of the pulsed microwave radiation and parameters of laser excitation of the initial ${37P}_{3/2}$ state. The quantum beats of magnetic sublevels appeared in the signals when the polarization of exciting laser emission was orthogonal to the magnetic field, and the interference occurred in the scheme of transitions similar to the Mach-Zehnder optical interferometer.

The pulsed-field recombination scheme is used to recombine free electrons with ${\mathrm{Li}}^{+}$ ions to produce neutral Li atoms in a high Rydberg state $\left(n\approx 180\right).$ The experimental conditions are similar to the conditions under which antiprotons and positrons are recombined to produce cold antihydrogen. In the current experiments we have trapped electrons in a Penning trap $\left(B\approx 35\mathrm{mT}\right).\mathrm{}$ Subsequently these electrons were recombined with spatially separated ${\mathrm{Li}}^{+}$ ions. The recorded efficiency is 2.0% versus 0.3% in previous experiments with atomic ions. Several experiments and simulations were performed to study the dynamics of pulsed-field recombination in more detail.

We consider a time-dependent nonlinear Schrödinger equation in one dimension (1D) with a fifth-order interaction term and external harmonic confinement, as a model for both (i) a Bose gas with hard-core contact interactions in the local-density approximation, and (ii) a spin-polarized Fermi gas in the collisional regime. We evaluate analytically in the Thomas-Fermi limit the density fluctuation profiles and the collective excitation frequencies, and compare the results for the low-lying modes with those obtained from numerical solution of the Schrödinger equation. We find that the excitation frequencies are multiples of the harmonic-trap frequency even in the strong-coupling Thomas-Fermi regime. This result shows that the hydrodynamic and the collisionless collective spectra coincide in the harmonically confined 1D Fermi gas, as they do for sound waves in its homogeneous analog. It also shows that in this case the local-density theory reproduces the exact collective spectrum of the hard-core Bose gas under harmonic confinement.

An extensive characterization of high-finesse optical cavities used in cavity QED experiments is described. Different techniques in the measurement of the loss and phase shifts associated with the mirror coatings are discussed and their agreement shown. Issues of cavity-field mode structure supported by the dielectric coatings are related to our effort to achieve the strongest possible coupling between an atom and the cavity.

We present a tomographic reconstruction procedure that exploits the symmetry of the SU(1,1) group existing in some physical systems. The tomographic algorithm is derived analytically and the convergence of the procedure is tested on Monte Carlo simulated data.

We demonstrate that the negative amplitude gain in a photorefractive two-wave-mixing experiment under applied electric field measurably reduces the characteristic instability of the recorded hologram. In this sense photorefractive materials behave like electronic amplifiers with feedback. We analyze the case of stationary and running holograms both under an externally applied electric field. A continuous phase-modulation method is used to simultaneously measure diffraction efficiency and phase shift. Measurements carried out on a ${\mathrm{Bi}}_{12}{\mathrm{TiO}}_{20}$ crystal at 514.5 nm wavelength confirm the occurrence of continuous oscillations in both the diffraction efficiency and the phase shift. The perturbations in the diffraction efficiency increase considerably with increasing applied field and are reduced when energy is transferred from the weaker to the stronger beam (negative gain). Our results indicate that the perturbations in our experiments are probably due to resonantly excited transient effects.

The local optical density of states (LDOS) in 340-nm-diam ${\mathrm{SiO}}_2$ spherical microcavities was calculated and probed experimentally by measuring the luminescence decay rate at 1.54 μm of erbium ions implanted in the colloids. To separate the effect of nonradiative processes, first the radiative decay rate of ${\mathrm{Er}}^{3+}$ in bulk ${\mathrm{SiO}}_2$ was determined. This was done by varying the LDOS in an Er-doped planar ${\mathrm{SiO}}_2$ film by bringing the film into contact with liquids of different refractive index in the range $n=1.33\mathrm{}–\mathrm{1.57.}$ By comparing the calculated LDOS with the observed changes in decay rate with index, the radiative rate was found to be $54\pm 10{\mathrm{s}}^{\mathrm{-}1}$ $(\tau =18\mathrm{}\pm 3\mathrm{ms})$ in bulk ${\mathrm{SiO}}_2.$ This value was then used to analyze the difference in decay rate in colloids surrounded by air or immersed in an index-matching liquid. Within the experimental error, agreement was found between the calculated and experimentally probed LDOS in the colloids. Finally, a full determination of the LDOS vs size in ${\mathrm{SiO}}_2$ microcavities is presented $(2\mathrm{}\pi R/\lambda =0.1\mathrm{}–6.9),$ which shows the appearance of a number of maxima, corresponding to the position of the electric-type resonances inside the microcavity.

We add memory effects to the master equation describing a harmonic oscillator embedded in a reservoir. Solving the time evolution exactly, we show that the model is sensible only in the Markovian limit. Thus we issue a warning against indiscriminate introduction of memory effects in master equations and call for a systematic method to obtain corrections to Markovian time evolution.

We formulate continuous variable quantum teleportation on a coherent-state basis. We present low-dimensional coherent state representation of the quadrature Bell states. This approach turns out to be suitable for investigating the teleportation process, yielding a simple direct description.

We have observed thermalization by elastic collisions of magnetically trapped metastable helium atoms. Our method directly samples the reconstruction of a thermal energy distribution after the application of a RF knife. The relaxation time of our sample toward equilibrium gives an elastic collision rate constant of $\alpha \sim 5\times {10}^{-9}\hspace{0.5em}{\mathrm{cm}}^3/\mathrm{s}$ at a temperature of 1 mK. This value is close to the unitarity limit.

A simple Hamiltonian determines in closed form the potential of the long-range force between two fixed molecules polarizable magnetically as well as electrically, exposed to blackbody radiation at temperature T. The results apply provided $\mathrm{kT}\ll ħ\Omega$ and at separations $\rho \gg c/\Omega ,$ with ħΩ a typical molecular excitation energy.

The quantum-electrodynamic Helmholtz free energy of binding, at temperature T, is determined perturbatively to order $(n\alpha {)}^2$ for atomic solid spheres of radius a, having dielectric constant $\varepsilon \simeq 1+4\pi n\alpha$ and magnetic susceptibility either $\mu =1\mathrm{}$ or $\mu =1/\varepsilon \simeq 1-4\pi n\alpha .$ Here n is the number density, and the atomic polarizabilty α is taken as independent of frequency. The perturbative shifts are regularized by disallowing atomic separations below some minimum λ; they are renormalized by dropping components proportional to the volume and surface area, and the renormalized shifts $\Delta B/(n\alpha {)}^2$ are expressed in terms of moments of the interatomic potential W at given T, quoted from the preceding paper. Such shifts are always dominated by (nominally) divergent components of order $-ħc/\lambda ,$ independent of T and a. For $kTa/ħc\gg 1,$ the convergent terms are of order $-\mathrm{kT}\ln (kTa/ħc);$ for $kTa/ħc\ll 1,$ they are of order $-(kTa/ħ{c)}^3(ħc/a)$ when $\mu =1\mathrm{}$ and of order $-(kTa/ħ{c)}^4(ħc/a)$ when $\mu =1/\varepsilon .$ There is no compelling reason why these convergent terms should be exactly the same as the shifts determined by recent normal-mode summations; nevertheless, agreement is complete for $\mu =1/\varepsilon$ and almost complete for $\mu =1.\mathrm{}$

We explore the effects of ultrafast shaped pulses for two-level systems that do not have a single-photon resonance, by developing a multiphoton density-matrix approach. We take advantage of the fact that the dynamics of the intermediate virtual states are absent within our laser pulse time scales. Under these conditions, the multiphoton results are similar to those for a single photon, and it is possible to extend the single-photon coherent control ideas to develop multiphoton coherent control.

We consider a harmonically trapped few-boson system under rotation and investigate the ground-state properties beyond the usual “lowest-Landau-level” approximation by using exact diagonalizations in a restricted Hilbert subspace. We find that both the effective interaction energy and density distribution are strongly affected by the two-body interaction strength.