The radiative decay rates of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level in neonlike ions have been calculated for nuclear charges ranging from $Z=10$ to $Z=110$. The calculations include the magnetic dipole decay to the $(2s^{2}2p_{3/2}^{5}3s_{1/2}){}_{J=1}$ level, which is shown to be the dominant decay branch in low-$Z$ and very-high-$Z$ ions, as well as the two-electron, one-photon decays to the $(2s^{2}2p_{3/2}^{5}3p_{1/2}){}_{J=1}$ and $(2s^{2}2p_{3/2}^{5}3p_{3/2}){}_{J=1}$ levels, which dominate near $Z=50$. We also take into account a small magnetic quadrupole decay branch to the $(2s^{2}2p_{3/2}^{5}3s_{1/2}){}_{J=2}$ level and calculate the total radiative lifetime of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level. The resulting values span over 15 orders of magnitude, and much of this range is accessible with modern atomic lifetime measurement techniques. In particular, we calculate a value of $1.6\times {10}^4$ ${\mathrm{s}}^{-1}$ for the radiative decay rate of the $(2s^{2}2p_{1/2}^{5}3s_{1/2}){}_{J=0}$ level in Fe XVII and show that the corresponding magnetic dipole transition has a measurable spectral intensity for electron densities below about $1\times {10}^{13}$ cm${}^{-3}$.

Fivefold differential cross sections for electron-induced double ionization of isolated oriented water molecules are reported. The theoretical investigation is performed within the first Born approximation by describing the initial molecular state by means of single-center wave functions. The contributions of each final state to the double-ionization process, i.e., with target electrons ejected from similar and/or different molecular subshells, are studied and compared in terms of shape and magnitude. Furthermore, for the particular target orientations investigated, we identify clearly the signature of the main scenarios involved in (e,3e) reactions, namely, the shake-off and the two-step 1 mechanisms.

Coherent control of quantum tunneling is investigated for a single atom held in a driven triple-well potential without tight-binding approximation. In the high-frequency regime within or without multiphoton resonance, we find the analytical solutions and their numerical correspondences, including the special Floquet states of invariant populations and the non-Floquet states of slowly varying populations. The Floquet quasienergy spectrum exhibits anticrossings and crossings for different values of the driving parameters, which are associated with different tunneling properties described by the non-Floquet states. Applying the presented results, we suggest a scheme for transporting a single atom between nonadjacent wells or between adjacent wells.

We investigate nonsequential double ionization (NSDI) of helium by using an additional magnetic field parallel to the polarization of the laser pulse. By exploring the ability of a magnetic field for focusing the selected trajectories that contribute to the NSDI, we have found that the yield of NSDI, as a function of the magnetic-field strength, shows different behavior for different laser intensities. As a result, an additional magnetic field provides a way to identify that the NSDI mechanism of laser-assisted collision ionization begins to play an important role as the laser intensity increases.

We compare strong-field ionization probabilities of ${\mathrm{N}}_2$ and ${\mathrm{F}}_2$ molecules using time-dependent density functional theory calculations. Accurate nuclear potentials and ground vibrational wave functions are incorporated into our study. For both molecules, the effect of molecular vibration is small, while that of the molecular orientation is significant. When compared to the ionization probability of a molecule at the equilibrium geometry, we estimate the effect of the ground state vibration to be within 3% for ${\mathrm{N}}_2$ and within 6% for ${\mathrm{F}}_2$ in the intensity range from 1 to $5\times {10}^{14}$ W/cm${}^2$. The molecular-orientation–dependent ionization probabilities for both molecules at various intensities are presented. They are strongly dependent on the laser intensity, and the anisotropy diminishes when the laser intensity is high. For laser intensities of 1.6 and $2.2\times {10}^{14}$ W/cm${}^2$ we find ionization probability ratios of 5.9 and 4.3, respectively, for the parallel versus perpendicular orientation of ${\mathrm{N}}_2$. This is reasonably consistent with experimental measurements. For randomly oriented molecules, the ratio of the probabilities for ${\mathrm{N}}_2$ and ${\mathrm{F}}_2$ increases from about 1 at ${10}^{14}$ W/cm${}^2$ to 2 at $4\times {10}^{14}$ W/cm${}^2$, which agrees well with experimental results.

We consider a Bose-Einstein condensate, described by the Gross-Pitaevskii equation, in a horizontally vibrating shallow optical lattice. We study the dynamics of a bright soliton using the collective coordinate approximation. We show that depending on the parameters, amplitude, and frequency of the vibration of the lattice, the phase space of the equation of motion for the soliton center of mass shows multistability. In the frequency locked regions, in which the soliton has a nonzero average velocity determined by the external frequency, the motion is quasiperiodic, and between the locked regions the soliton moves chaotically.

We describe the transition of $N$ weakly interacting atoms into a Bose-Einstein condensate within a number-conserving quantum master equation theory. Based on the separation of time scales for condensate formation and noncondensate thermalization, we derive a master equation for the condensate subsystem in the presence of the noncondensate environment under the inclusion of all two-body interaction processes. We numerically monitor the condensate particle number distribution during condensate formation, and derive a condition under which the unique equilibrium steady state of a dilute, weakly interacting Bose-Einstein condensate is given by a Gibbs-Boltzmann thermal state of $N$ noninteracting atoms.

We find nearly all the exact ground states of a mixture of two species of spin-1 atoms with both interspecies and intraspecies spin exchanges in the absence of a magnetic field. The quantum phase diagram in the three-dimensional parameter space and its two-dimensional cross sections are described. The boundaries where the ground states are either continuous or discontinuous are determined, with the latter identified as where quantum phase transitions take place. The two species are always disentangled if the interspecies spin coupling is ferromagnetic or zero. Quantum phase transitions occur when the interspecies spin coupling varies between antiferromagnetic and zero or ferromagnetic while the two intraspecies spin couplings both remain ferromagnetic. On the other hand, by tuning the interspecies spin coupling from zero to antiferromagnetic and then back to zero, one can circumvent the quantum phase transition due to sign change of the intraspecies spin coupling of a single species, which is spin decoupled with the other species with ferromagnetic intraspecies spin coupling. Generally speaking, interplay among interspecies and two intraspecies spin exchanges significantly enriches quantum phases of spinor atomic gases.

We study the local correlations in the super Tonks-Girardeau gas, a highly excited, strongly correlated state obtained in quasi-one-dimensional Bose gases by tuning the scattering length to large negative values using a confinement-induced resonance. Exploiting a connection with a relativistic field theory, we obtain results for the two-body and three-body local correlators at zero and finite temperature. At zero temperature, our result for the three-body correlator agrees with the extension of the results of Cheianov et al. [Phys. Rev. A 73, 051604(R) (2006)], obtained for the ground state of the repulsive Lieb-Liniger gas, to the super-Tonks-Girardeau state. At finite temperature, we obtain that the three-body correlator has a weak dependence on temperature up to the degeneracy temperature $T_{\mathrm{D}}$. We also find that, for temperatures larger than $T_{\mathrm{D}}$, the values of the three-body correlator for the super-Tonks-Girardeau gas and the corresponding repulsive Lieb-Liniger gas are rather similar, even for relatively small couplings.

We used the Gross-Pitaevskii equations to investigate ferromagnetic resonance in spin-1 Bose-Einstein condensates with a magnetic dipole-dipole interaction. By introducing the dipole interaction, we obtained equations similar to the Kittel equations used to represent ferromagnetic resonance in condensed-matter physics. These equations indicated that the ferromagnetic resonance originated from dipolar interaction, and that the resonance frequency depended upon the shape of the condensate. Furthermore, spin currents driven by spin diffusions are characteristic of this system.

We investigate the dynamics of a wave packet in a parity-breaking one-dimensional periodic potential slowly varied in time and perturbed by a linear potential. Parity is broken by considering an asymmetric double well per unit cell. By comparing the prediction of the semiclassical dynamics with the full Schrödinger solution, we show that Bloch oscillations are strongly affected by anomalous velocity corrections related to Berry’s phase. We characterize how these effects depend on the degree of parity breaking of the potential and on the modulation parameters. We also discuss how to measure the effects of the anomalous velocity in current experiments with noninteracting Bose-Einstein condensates in bichromatic optical lattices, under the effect of gravity.

We use entanglement to investigate the transition from vortex-liquid phase to vortex-lattice phase in a weakly interacting rotating Bose-Einstein condensate. For the torus geometry, the ground-state entanglement spectrum is analyzed to distinguish these two phases. The low-lying part of the ground-state entanglement spectrum, as well as the behavior of its lowest level, changes clearly when the transition occurs. For the sphere geometry, the entanglement gap in the conformal limit is also studied. We also show that the decrease in entanglement between particles can be regarded as a signal of the transition.

High-order harmonic generation (HHG) in carbon-nanotube (CNT)-containing plasma plumes has been demonstrated. Various targets were ablated to produce the plasma plumes containing nanotubes for the HHG in these media. Harmonics up to the 29th order were generated. Odd and even harmonics were generated using a two-color pump. The integrity of CNTs within the plasma plume, indicating nanotubes as the source of high-order harmonics, was confirmed by structural studies of plasma debris.

By solving the time-dependent Schrödinger equation nonperturbatively by the state-specific expansion approach, we have obtained reliable results showing the dependence of the formation of the excitation profile of the autoionizing state He ${}^{\prime }2s2p{}^{\prime }$ ${}^1{P}^o$ for Gaussian pulses of intensities in the range $I\approx {10}^{10}\hspace{0.5em}\mathrm{W}/{\mathrm{cm}}^2$ to $I\approx {10}^{15}\hspace{0.5em}\mathrm{W}/{\mathrm{cm}}^2$, and of duration 100–2 fs. Conclusions are drawn as regards the breakdown of first-order time-dependent perturbation theory.

Extensive configuration interaction calculations for the $2s^{2}2p-2s2p^2$ transitions for several ions along the B I isoelectronic sequence (Al ix, Mn xxi, Fe xxii, Co xxiii, Ni xxiv, Cu xxv, Zn xxvi, Mo xxxviii, and Au lxxv) have been calculated using the grasp2 k package based on the multiconfiguration Dirac-Hartree-Fock (MCDHF) method. By employing active-space techniques to expand the configuration list, we also included Breit interaction and quantum electrodynamical (QED) effects to correct atomic state wave functions and the corresponding energies. Both valence correlation and core polarization effects are included, the latter being significant in achieving agreement between length and velocity forms of the oscillator strengths of related allowed transitions. The fine-structure energy levels, term splitting, transition energies, transition rates, line strengths, and thereby the branching ratios are compared with experimental data and with values from other calculations.

We present the design and operation of an ytterbium ion trap experiment with a setup offering versatile optical access and 90 electrical interconnects that can host advanced surface and multilayer ion trap chips mounted on chip carriers. We operate a macroscopic ion trap compatible with this chip carrier design and characterize its performance, demonstrating secular frequencies $>$1 MHz, and trap and cool nearly all of the stable isotopes, including ${}^{171}\mathrm{Yb}$${}^{+}$ ions, as well as ion crystals. For this particular trap we measure the motional heating rate $\langle \mathrm{ṅ}\rangle$ and observe an $\langle \mathrm{ṅ}\rangle \propto 1/{\omega }^2$ behavior for different secular frequencies $\omega$. We also determine a spectral noise density $S_E(1\hspace{0.5em}\mathrm{MHz})=3.6(9)\times {10}^{-11}$ ${\mathrm{V}}^2$ ${\mathrm{m}}^{-2}$ Hz${}^{-1}$ at an ion electrode spacing of 310(10) $\mu$m. We describe the experimental setup for trapping and cooling Yb${}^{+}$ ions and provide frequency measurements of the ${}^2{S}_{1/2}{\leftrightarrow }^2$$P_{1/2}$ and ${}^2{D}_{3/2}{\leftrightarrow }^3$$D[3/2]{}_{1/2}$ transitions for the stable ${}^{170}\mathrm{Yb}$${}^{+}$, ${}^{171}\mathrm{Yb}$${}^{+}$, ${}^{172}\mathrm{Yb}$${}^{+}$, ${}^{174}\mathrm{Yb}$${}^{+}$, and ${}^{176}\mathrm{Yb}$${}^{+}$ isotopes which are more precise than previously published work.

We study the stimulated Raman adiabatic passage technique in an $N$-pod system driven by $N$ pulsed fields when $N-2$ and $N-1$ pulses not connected to the initial state have the same shape. We show that, for properly timed pulses, robust population transfer from an initial ground state to an arbitrary coherent superposition of the ground states can be achieved in a single step. The case of $N-2$ pulses of the same shape involves a geometric phase of the same type as the one appearing in tripod systems.

We present an investigation of electromagnetically induced transparency (EIT) without Doppler background due to a locked probe laser. The EIT is theoretically studied based on a multilevel ladder-type cesium atomic system 6$S_{1/2}$–6$P_{3/2}$–8$S_{1/2}$ in a room-temperature vapor cell. The experimental results agree with the theoretical calculations. Compared with the traditional EIT spectra with a Doppler profile limiting the spectral resolution for keeping the coupling laser locked and scanning the probe laser, these EIT spectra with the probe laser locked and the coupling laser scanned have a flat background, which seem be of great benefit for applications such as the measurement of hyperfine intervals between excited states, the study of highly excited Rydberg states, laser-frequency stabilization, etc.

We investigate the dynamical Casimir effect and its detection with Rydberg atoms. The photons are created in a resonant cavity with a plasma mirror of a semiconductor slab which is irradiated by periodic laser pulses. The canonical Hamiltonian is derived for the creation and annihilation operators, showing the explicit time variation in the couplings, which originates from the external configuration such as a nonstationary plasma mirror. The number of created photons is evaluated as squeezing from the Heisenberg equations with the Hamiltonian. Then the detection of the photons as the atomic excitations is examined through the atom-field interaction. Some consideration is made for a feasible experimental realization with a semiconductor plasma mirror.