The electronic stress tensor of the hydrogen molecule ion $\text{H}^{+}{}_2$ is investigated for the ground state $\left({\sigma }_{g}1s\right)$ and the first excited state $\left({\sigma }_u^{\ast }1s\right)$ using their exact wave functions. A map of its largest eigenvalue and corresponding eigenvector is shown to be closely related to the nature of chemical bonding. For the ground state, we also show the spatial distribution of interaction energy density to describe in which part of the molecule stabilization and destabilization take place.

We present experimental cross-section measurements for electron-impact excitation from the ground level and from the $\text{Xe}\left(5p^{5}6s\right)J=2$ metastable level into levels of the $\text{Xe}\left(5p^{5}7p\right)$ manifold using the optical method. The magnitudes of cross sections for excitation out of the ground-state range from $\left(65–365\right)\times {10}^{-20}{\text{cm}}^2$. Cross sections out of the ground level are also investigated for pressures ranging from 0.1–1.0 mTorr, and show moderate dependence (particularly at high energies) on pressure due to cascades from resonant levels. Cross sections for excitation out of the metastable level have peak magnitudes that are on average more than an order of magnitude larger than their ground-state counterparts. Furthermore, cross sections out of the metastable levels into the $\text{Xe}\left(5p^{5}7p\right)$ levels as a function of energy display a surprising variety of shapes which are discussed in relation to oscillator strengths. Together, the ground state and metastable cross sections measured in this work are expected to be useful for optical diagnostics of plasmas containing xenon.

Electron impact coherence parameters for inelastic $e\text{-He}$ scattering have been measured for the excitation to the $2{{}^1\text{P}}_1$ state at collision energy of 100 eV. The experiment was conducted using angular correlation electron-photon coincidence technique with a magnetic angle changer allowing measurements in full range of scattering angles. The results are compared with other experimental data and theoretical predictions available for this collisional system.

We report cross sections for elastic collisions of low-energy electrons with the ${\text{CH}}_2{\text{O-H}}_2\text{O}$ complex. We employed the Schwinger multichannel method with pseudopotentials in the static-exchange and in the static-exchange-polarization approximations for energies from 0.1 to 20 eV. We considered four different hydrogen-bonded structures for the complex that were generated by classical Monte Carlo simulations. Our aim is to investigate the effect of the water molecule on the ${\pi }^{\ast }$ shape resonance of formaldehyde. Previous studies reported a ${\pi }^{\ast }$ shape resonance for ${\text{CH}}_2\text{O}$ at around 1 eV. The resonance positions of the complexes appear at lower energies in all cases due to the mutual polarization between the two molecules. This indicates that the presence of water may favor dissociation by electron impact and may lead to an important effect on strand breaking in wet DNA by electron impact.

We report investigations of the spin-asymmetry function $S_{\text{A}}$ in elastic electron scattering from lead atoms. The experimental results are compared to previous measurements as well as to earlier and recent relativistic model-potential and $R$-matrix (close-coupling) calculations. The spin-asymmetry function is found to depend strongly on the incident-electron energy in the region between 11 and 14 eV.

We present a theoretical description of dissociative recombination of triatomic molecular ions having large permanent dipole moments. The study has been partly motivated by a discrepancy between experimental and theoretical cross sections for dissociative recombination of the ${\text{HCO}}^{+}$ ion. The ${\text{HCO}}^{+}$ ion has a considerable permanent dipole moment $\left(D\approx 4\text{D}\right)$, which has not been taken explicitly into account in previous theoretical studies. In the present study, we include explicitly the effect of the permanent electric dipole on the dynamics of the incident electron using the generalized quantum defect theory, and we present the resulting cross section obtained. This demonstrates the possibility of applying generalized quantum defect theory to the dissociative recombination of molecular ions.

We present an approach to calculating strong field ionization dynamics of multielectron molecular targets. Adopting a multielectron wave function ansatz based on field-free ab initio neutral and ionic multielectron states, a set of coupled time-dependent single-particle Schrödinger equations describing the neutral amplitude and continuum electron are constructed. These equations, amenable to direct numerical solution or further analytical treatment, allow one to study multielectron effects during strong field ionization, recollision, and high-harmonic generation. We apply the method to strong field ionization of ${\text{CO}}_2$ and suggest the importance of intermediate core excitation to explain the previous failure of analytical models to reproduce experimental ionization yields for this molecule.

We demonstrate a high level of laser-induced transient alignment in room temperature and density ${\text{N}}_2$ with a technique that avoids laser field ionization. Our measured alignment shows an improvement over previous one-pulse or two-pulse experimental alignment results and approaches the theoretical maximum value. We employ eight equally spaced ultrafast laser pulses with a separation that takes advantage of the periodic revivals for the ensemble of quantum rotors. Each successive pulse increases the transient alignment $\left[⟨{\text{cos}}^2\theta ⟩\left(t\right)\right]$ and also moves the rotational population away from thermal equilibrium. These measurements are combined with simulations to determine the value of $⟨{\text{cos}}^2\theta ⟩$, the $J$-state distributions, and the functional dependencies of the alignment features.

We apply the convergent close-coupling (CCC) formalism to single-photon two-electron ionization of the lithium atom in its ground state. We treat this reaction as single-electron photon absorption followed by inelastic scattering of the photoelectron on a heliumlike ${\text{Li}}^{+}$ ion. The latter scattering process can be described accurately within the CCC formalism. We obtain integrated cross sections of single photoionization leading to the ground and various excited states of the ${\text{Li}}^{+}$ ion as well as double photoionization extending continuously from the threshold to the asymptotic limit of infinite photon energy. Comparison with available experimental and theoretical data validates the CCC model.

Two nonperturbative approaches are used to calculate the total cross sections for the double photoionization of Li from its ground and first excited states. From the ground state, both the time-dependent close coupling and $R$ matrix with pseudostate approaches find reasonable agreement with experimental data, and from the first excited state (where no measurements are available), the two approaches are also in reasonable agreement.

We investigate the generation of bright correlated anti-Stokes and Stokes light beams with Doppler-broadened four-level atoms inside an optical ring cavity. By manipulating the large dispersion of the intracavity atomic medium near the electromagnetically induced transparency condition, the generated anti-Stokes and Stokes light fields can be made simultaneously on resonance with the cavity and to oscillate above threshold with narrowed linewidths. Noise correlation and violation of the Cauchy-Schwarz inequality with the two generated twin beams above the oscillation threshold at zero time delay are experimentally demonstrated.

We investigate the stability of Bloch waves for a Bose-Einstein condensate moving through a periodic lattice which is created by another condensate modulated by an optical lattice. We show that the coupling of phonon-antiphonon modes of the two species gives rise to a very rich structure of the regimes for dynamical instability, with significant differences with respect to the case of a single condensate in an optical lattice. We characterize the relative weight of each condensate in the mixing and discuss an analytic limit that accounts for the bare structure of the instability diagrams.

We propose to utilize density distributions from a series of time-of-flight images of an expanding cloud to reconstruct single-particle correlation functions of trapped ultracold atoms. In particular, we show how this technique can be used to detect off-diagonal correlations of atoms in a quasi-one-dimensional trap, where both real- and momentum-space correlations are extracted at a quantitative level. The feasibility of this method is analyzed with specific examples, taking into account finite temporal and spatial resolutions in experiments.

We describe the design and function of a circular magnetic waveguide produced from wires on a microchip for atom interferometry using de Broglie waves. The guide is a two-dimensional magnetic minimum for trapping weak-field seeking states of atoms or molecules with a magnetic dipole moment. The design consists of seven circular wires sharing a common radius. We describe the design, the time-dependent currents of the wires and show that it is possible to form a circular waveguide with adjustable height and gradient while minimizing perturbation resulting from leads or wire crossings. This maximal area geometry is suited for rotation sensing with atom interferometry via the Sagnac effect using either cold atoms, molecules and Bose-condensed systems.

We determine the conditions under which topological order survives a rapid quantum quench. Specifically, we consider the case where a quantum spin system is prepared in the ground state of the toric code model and, after the quench, it evolves with a Hamiltonian that does not support topological order. We provide analytical results supported by numerical evidence for a variety of quench Hamiltonians. The robustness of topological order under nonequilibrium situations is tested by studying the topological entropy and a dynamical measure, which makes use of the similarity between partial density matrices obtained from different topological sectors.

Dispersive shock waves (DSWs) are studied theoretically in the context of two-dimensional (2D) supersonic flow of a superfluid. Employing Whitham averaging theory for the repulsive Gross-Pitaevskii (GP) equation, suitable jump and entropy conditions are obtained for an oblique DSW, a fundamental building block for 2D flows with boundaries. In analogy to oblique viscous shock waves (VSWs), these conditions yield analytic relations between Mach number $\left(M\right)$, velocity deflection angle $\left(\theta \right)$, and wave angle $\left(\beta \right)$. Unlike VSWs, the $M\text{−}\theta \text{−}\beta$ phase diagram for DSWs displays four distinct regions associated with phase transitions in supersonic flow over a corner which are predicted and verified by numerical computations of the GP equation. Quasistationary DSWs, shock detachment due to transonic flow, spontaneous excitation of vortices, and the onset of turbulent dynamics associated with cavitation of the superfluid are observed.

It is shown that the jump in the momentum distribution of Fermi gases evolves smoothly for small and intermediate times once an interaction between the fermions is suddenly switched on. The jump does not vanish abruptly. The loci in momentum space where the jumps occur are those of the noninteracting Fermi sea. No relaxation of the Fermi surface geometry takes place.

We analyze the dynamical behavior of a quantum system under the actions of two counteracting baths: the inevitable energy draining reservoir and, in opposition, exciting the system, an engineered Glauber’s amplifier. We follow the system dynamics towards equilibrium to map its distinctive behavior arising from the interplay of attenuation and amplification. Such a mapping, with the corresponding parameter regimes, is achieved by calculating the evolution of both the excitation and the Glauber-Sudarshan $P$ function. Techniques to compute the decoherence and the fidelity of quantum states under the action of both counteracting baths, based on the Wigner function rather than the density matrix, are also presented. They enable us to analyze the similarity of the evolved state vector of the system with respect to the original one, for all regimes of parameters. Applications of this attenuation-amplification interplay are discussed.

The quantized surface mode technique is used to calculate the Casimir torque between two parallel anisotropic metamaterial plates with in-plane optical axes, and our main concern is focused on the impact of the magnetic properties of the plates on the Casimir torque. Our result shows that at small separation, the Casimir torque between the two plates with frequency dependent permeabilities is larger than that between two nonmagnetic plates, while at large separation it is smaller. This can be explained as a result of the impact of both magnetic properties and material dispersion of the plates. The impact of the Drude background in connected metallic metamaterial is also discussed. These phenomena provide us with new understanding about the Casimir effect and show great potential in application.

We propose a quantum storage scheme independent of the current time-control schemes and study a “quantum data bus” (transmission line resonator) in a hybrid system consisting of a circuit QED system integrated with a cold molecular ensemble. Here, an effective interaction between the charge qubit and molecules is mediated by the off-resonant field in the data bus. Correspondingly, the charge state can be mapped into the collective quasispin state of the molecular ensemble via the standard dark-state-based adiabatic manipulation.