For the principal isotopologue ${}^{14}\mathrm{N}$${}^{32}\mathrm{S}$${}^{19}\mathrm{F}$${}_3$ of thiazyl trifluoride in the degenerate fundamental state ($v_5=1$), the hyperfine structure has been investigated in the $\mathit{Q}$-branch spectrum between 8 and 26.5 GHz using microwave Fourier transform waveguide spectrometers with a resolution limit of $\approx$30 kHz. In addition to $\mathit{l}$-type doubling spectra and $\mathit{l}$-type resonance transitions with ($\Delta k=\Delta l=\pm 2$), perturbation-allowed spectra were measured with $\Delta (k-l)=\pm 3,\pm 6$. The range in $\mathit{J}$ was from 13 to 61; for the lower states, $\mathit{kl}=-3,-2,-1,0,+1$. For all the transitions, the hyperfine patterns observed are predicted to be doublets when only the nitrogen quadrupole Hamiltonian ${\mathbf{H}}_Q^{\mathrm{N}}$ is taken into account. Doublets were indeed measured for transitions with ${\Gamma }_{\mathrm{RV}}=A_1\leftrightarrow A_2$, where ${\Gamma }_{\mathrm{RV}}$ is the rovibrational symmetry. However, when ${\Gamma }_{\mathrm{RV}}=E\leftrightarrow E$, triplets and quartets were observed in addition to doublets. These anomalous hyperfine patterns are shown to be due to the ($\Delta k=\pm$1) and ($\Delta k=\pm$2) matrix elements of the fluorine spin-rotation Hamiltonian ${\mathbf{H}}_{\mathrm{SR}}^{\mathrm{F}}$ characterized by the fluorine spin-rotation constants $c(1)=\frac{1}{2}(c_{\mathit{xz}}+c_{\mathit{zx}}^{*})$ and $c(2)=\frac{1}{2}(c_{\mathit{xx}}-c_{\mathit{yy}})$, respectively. These terms in ${\mathbf{H}}_{\mathrm{SR}}^{\mathrm{F}}$ lift the parity degeneracy for ${\Gamma }_{\mathrm{RV}}=E$. The rovibrational Hamiltonian H${}_{\mathrm{RV}}$ was adopted from an earlier partner study [S. Macholl et al., J. Phys. Chem. A 113, 668 (2009)]. A good fit to the hyperfine data was obtained with a standard deviation of 3.1 kHz. In the fitting process, 12 rovibrational parameters were varied, while the remaining constants in H${}_{\mathrm{RV}}$ were left at the values of Macholl et al. In addition, six hyperfine parameters were determined: four in ${\mathbf{H}}_Q^{\mathrm{N}}$, and two in ${\mathbf{H}}_{\mathrm{SR}}^{\mathrm{F}}$. It was found that $|c(1)|=7.48(24)$ kHz and $|c(2)|=2.423(22)$ kHz. This determination of $\mathit{c}(1)$ is the first to be reported based on frequency measurements. In all the previous detections of parity doubling where the splittings were accounted for quantitatively, the levels involved had $K=\left|k\right|=1$ in studies of the ground vibrational state or $G\equiv |k-l|=1$ in investigations of degenerate vibrational states. In the current work, several different values of $\mathit{G}$ were involved, thus demonstrating experimentally for the first time that this splitting process is a general phenomenon. The key to the observation of the parity doubling lies in the regional resonances discovered by Macholl et al. The clustering of rovibrational levels at low $\mathit{K}$ leads to severe mixing. For each eigenstate involved in a regional resonance, the eigenstate consists of a linear superposition of basis vectors with several different values of $\mathit{kl}$ having sizable expansion coefficients. As a result, the ($\Delta k=\pm 1,\pm$2) matrix elements of ${\mathbf{H}}_{\mathrm{SR}}^{\mathrm{F}}$ that typically connect levels widely separated in energy occur here effectively on the diagonal, thereby greatly enhancing the effects of $\mathit{c}(1)$ and $\mathit{c}(2)$. These spin-rotation matrix elements are derived here for ${\Gamma }_{\mathrm{RV}}=E$ in the low-field representation.

A relaxed form of a recent impact parameter coupled pseudostate approximation of McGovern et al. [Phys. Rev. A 79, 042707 (2009)] for calculating differential ionization cross sections is proposed. This greatly eases the computational burden in cases where a range of ejected electron energies has to be considered. The relaxed approximation is tested against exact first Born calculations for antiproton impact on H and nonperturbatively for the highly nonperturbative system of Au${}^{53+}$ incident upon He. The approximation performs well in these tests. It is shown how, with a little further approximation, the relaxed theory leads to a widely used prescription for the total ionization cross section. Results for differential ionization of H and He by antiprotons are presented. These reveal the growing dominance of the interaction between the antiproton and the target nucleus at low impact energies and show the changing importance of the role of the postcollisional interaction between the antiproton and the ejected electron.

Using measured spin-transfer rates from alkali-metal atoms to ${}^3\mathrm{He}$, combined with spin-relaxation rates of the alkali-metal atoms due to ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$, it should be possible to differentiate between isotropic and anisotropic spin exchange. This would give a fundamental limit on the ${}^3\mathrm{He}$ polarization attainable in spin-exchange optical pumping. For K-He, we find the limit to be $0.90\pm 0.11$.

In the strong field molecular tunneling ionization theory of Tong et al. [Phys. Rev. A 66, 033402 (2002)], the ionization rate depends on the asymptotic wave function of the molecular orbital from which the electron is removed. The orbital wave functions obtained from standard quantum chemistry packages in general are not good enough in the asymptotic region. Here we construct a one-electron model potential for several linear molecules using density functional theory. We show that the asymptotic wave function can be improved with an iteration method and after one iteration accurate asymptotic wave functions and structure parameters are determined. With the new parameters we examine the alignment-dependent tunneling ionization probabilities for several molecules and compare with other calculations and with recent measurements, including ionization from inner molecular orbitals.

We report magnetic trapping of Yb in the excited ${}^3{P}_2$ state. This state, with a lifetime of 15 s, could play an important role in studies ranging from optical clocks and quantum computation to the search for a permanent electric dipole moment. Yb atoms are first cooled and trapped in the ground state in a 399-nm magneto-optic trap. The cold atoms are then pumped into the excited state by driving the ${}^1{S}_0\to {}^3{P}_1\to {}^3{S}_1$ transition. Atoms in the ${}^3{P}_2$ state are magnetically trapped in a spherical quadrupole field with an axial gradient of 110 G/cm. We trap up to ${10}^6$ atoms with a lifetime of 1.5 s.

We report a simple method for trap parameter measurement by realizing forced harmonic oscillation in a magneto-optical trap (MOT). Through the resonance curve of the vibrational amplitude of the harmonic oscillation on the driving frequency of the laser intensity, we measured the damping coefficient and trap frequency of trapped atoms in the MOT under various conditions and compared them with those obtained from the parametric resonance. In particular, we report a significant effect of a transverse laser on one-dimensional harmonic oscillation. This effect is expected to explain the discrepancies in other previous experiments between the experimental and theoretical results.

The electron-nuclear dynamics of one-dimensional ${{\mathrm{H}}_2}^{+}$ molecular high harmonic generation is investigated by numerical integration of the non-Born-Oppenheimer time-dependent Schrödinger equation. It is found that the nuclear motion and electron ionization are more significant for the longer wavelength and the stronger intensity of the driving laser pulse. When the ground-state ${{\mathrm{H}}_2}^{+}$ molecule is driven by a short laser pulse (ten optical cycles in the calculations), a strong signature of nuclear motion is seen in the wavelength scaling ($800–2000$ nm) of harmonic yield, following a ${\lambda }^{-(7-8)}$ scaling law at a constant laser intensity. It is attributed to the fast ground-state depletion induced by the strong nuclear motion, when using the long wavelength. Consequently, the wavelength scaling gives an insight into the nuclear dynamics.

We study dipole oscillations in a general fermionic mixture. Starting from the Boltzmann equation, we classify the different solutions in the parameter space through the number of real eigenvalues of the small oscillations matrix. We discuss how this number can be computed using the Sturm algorithm and its relation with the properties of the Laplace transform of the experimental quantities. After considering two components in harmonic potentials having different trapping frequencies, we study dipole oscillations in three-component mixtures. Explicit computations are done for realistic experimental setups using the classical Boltzmann equation without intraspecies interactions. A brief discussion of the application of this classification to general collective oscillations is also presented.

We analyze the effects of roughness in the magnitude of the magnetic field produced by a current carrying microwire, which is caused by the geometric fluctuation of the edge of the wire. The relation between the fluctuation of the trapping potential and the height the atom trap lies above the wire is very well consistent with the experimental data when the colored noise with a finite correlation length is considered. On this basis, we generate the random potential and get the density distribution of the Bose-Einstein condensate (BEC) atoms by solving the Gross-Pitaevskii equation, which coincides well with the experimental image, especially in the number of fragmentations. The results help us further understand the nature of the fluctuation and predict its possible application in the precise measurement.

We analyze the physics of Faraday patterns in dipolar Bose-Einstein condensates. Faraday patterns can be induced in Bose-Einstein condensates by a periodic modulation of the system nonlinearity. We show that these patterns are remarkably different in dipolar gases with a roton-maxon excitation spectrum. Whereas for nondipolar gases the pattern size decreases monotonously with the driving frequency, patterns in dipolar gases present, even for shallow roton minima, a highly nontrivial frequency dependence characterized by abrupt pattern size transitions, which are especially pronounced when the dipolar interaction is modulated. Faraday patterns constitute, hence, an excellent tool for revealing the onset of the roton minimum, a key feature of dipolar gases.

Quantum states with non-Gaussian statistics generated by optical parametric oscillators (OPO) with fluctuating parameters are studied by means of the kurtosis excess of the external field quadratures. The field generated is viewed as the response of a nonlinear device to the fluctuations of pump laser amplitude and frequency, crystal temperature, and cavity detuning, in addition to quantum noise sources. The kurtosis excess has been evaluated perturbatively up to the third order in the strength of the crystal nonlinear coupling factor and the second order in the classical fluctuating parameters. Applied to the device described in Opt. Expr. 13, 948 (2005), the model has given values of the kurtosis excess in good agreement with the measured ones.

Alkaline-earth-metal-like atoms with ultranarrow transitions open the door to a new regime of cavity quantum electrodynamics. That regime is characterized by a critical photon number that is many orders of magnitude smaller than what can be achieved in conventional systems. We show that it is possible to achieve superradiance in steady state with such systems. We discuss the basic underlying mechanisms as well as the key experimental requirements.

We present a theoretical framework for studying spatially dependent absorption in a thermal vapor of multilevel atoms, of arbitrary optical thickness. The atomic state dynamics, governed by a standard atom-optical master equation, are self-consistently coupled to the axial evolution of the probe beam intensity and the effusive gas dynamics. We derive steady-state equations for the spatially varying distributions of atomic populations and the probe beam intensity. From the latter, absorption coefficients in both the saturated and unsaturated regimes can be calculated. We present solutions to the resulting equations at various levels of approximation, including an example of the full numerical solution of a saturated, optically thick vapor of three-level atoms, demonstrating a breakdown of Beer’s law, among other measurable effects.

Quantum fluctuations in the radiation pressure of light can excite stochastic motions of mechanical oscillators thereby realizing a linear quantum opto-mechanical coupling. When performing a precise measurement of the position of an oscillator, this coupling results in quantum radiation pressure noise. Up to now this effect has not been observed yet. Generally speaking, the strength of radiation pressure noise increases when the effective mass of the oscillator is decreased or when the power of the reflected light is increased. Recently, extremely light SiN membranes ($\approx$100 ng) with high mechanical $Q$ values at room temperature ($⩾$10${}^6$) have attracted attention as low thermal noise mechanical oscillators. However, the power reflectance of these membranes is much lower than unity ($<$0.4 at a wavelength of 1064 nm) which makes the use of advanced interferometer recycling techniques to amplify the radiation pressure noise in a standard Michelson interferometer inefficient. Here, we propose and theoretically analyze a Michelson-Sagnac interferometer that includes the membrane as a common end mirror for the Michelson interferometer part. In this topology, both power and signal recycling can be used even if the reflectance of the membrane is much lower than unity. In particular, signal recycling is a useful tool because it does not involve a power increase at the membrane. We derive the formulas for the quantum radiation pressure noise and the shot noise of an oscillator position measurement and compare them with theoretical models of the thermal noise of a SiN membrane with a fundamental resonant frequency of 75 kHz and an effective mass of 125 ng. We find that quantum radiation pressure noise should be observable with a power of 1 W at the central beam splitter of the interferometer and a membrane temperature of 1 K.

We use relativistic Hartree-Fock and configuration-interaction methods to calculate the dependence of transition frequencies for singly ionized cobalt on the fine structure constant. The results are to be used in the search for variation of the fine structure constant in quasar absorption spectra.

By utilizing refractive-index enhancement with vanishing absorption, a scheme is suggested that achieves giant Kerr nonlinearities between two weak laser beams. One application of this scheme is discussed and an all-optical distributed Bragg reflector is proposed that works at very low light levels.

We compute the ground-state energy of atoms and quantum dots with a large number $N$ of electrons. Both systems are described by a nonrelativistic Hamiltonian of electrons in a $d$-dimensional space. The electrons interact via the Coulomb potential. In the case of atoms ($d=3$), the electrons are attracted by the nucleus via the Coulomb potential. In the case of quantum dots ($d=2$), the electrons are confined by an external potential, whose shape can be varied. We show that the dominant terms of the ground-state energy are those given by a semiclassical Hartree-exchange energy, whose $N\to \infty$ limit corresponds to Thomas-Fermi theory. This semiclassical Hartree-exchange theory creates oscillations in the ground-state energy as a function of $N$. These oscillations reflect the dynamics of a classical particle moving in the presence of the Thomas-Fermi potential. The dynamics is regular for atoms and some dots, but in general in the case of dots, the motion contains a chaotic component. We compute the correlation effects. They appear at the order $N\ln N$ for atoms, in agreement with available data. For dots, they appear at the order $N$.

We present a percolation strategy based on multipartite measurements to propagate entanglement in quantum networks. We consider networks spanned on regular lattices whose bonds correspond to pure but nonmaximally entangled pairs of qubits, with any quantum operation allowed at the nodes. Despite significant effort in the past, improvements over standard (classical) percolation have been found for only a few lattices, often with restrictions on the initial amount of entanglement in the bonds. In contrast, multipartite entanglement percolation outperform the classical percolation protocols, as well as all previously known quantum ones, over the entire range of initial entanglement and for every lattice that we considered. Finally, we briefly show that our ideas also find application in noisy networks.

This work reports an enhanced polarization and mechanisms in optically pumped (OP) hyperpolarized ${}^3\mathrm{He}$ in the presence of ${}^4\mathrm{He}$. The cells contain Rb metal, 60-torr ${\mathrm{N}}_2$, and different pressures of ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$. In the absence of ${}^4\mathrm{He}$, the polarization of ${}^3\mathrm{He}$ increases monotonically from 4.5% to 8% when the pressure of ${}^3\mathrm{He}$ is increased from 300 to 1500 torr. In the presence of 1850-torr ${}^4\mathrm{He}$ gas, the polarization of ${}^3\mathrm{He}$ is enhanced from 7% to 30% for a cell containing 600-torr ${}^3\mathrm{He}$ and 60-torr ${\mathrm{N}}_2$. The wall relaxation factors $X$ for OP cells with and without buffering ${}^4\mathrm{He}$ gas were derived. It was found that the ${}^4\mathrm{He}$ gas confines the ${}^3\mathrm{He}$ atoms to a diffusion-limited region which effectively reduces the wall relaxation factor $X$. Mechanisms contributed to relaxation are addressed and discussed.

The frequency dependence of optical delays in both the wings and core of the cesium $6\hspace{0.5em}{}^2{S}_{1/2}-6\hspace{0.5em}{}^2{P}_{3/2}$ transition have been observed and modeled with a Voigt line shape convolved with the six hyperfine components. Tunable delays of $0-37$ ns are achieved by tuning the laser frequency through resonance at various vapor pressures of $0.15-5.28$ mTorr.