[en] High-resolution resonant Auger electron spectra of NO measured in the vicinity of the N 1s → 2π core excitations are presented. The open shell electronic configuration of the molecule results in four excited electronic states, three of which are populated in the photoabsorption spectrum, ²Δ, ²Σ^- and ²Σ⁺. Electron emission spectra obtained at different vibrational levels of the three N 1s core-excited states of NO are reported. Recently reported ab initio calculations [J. Chem. Phys. 106, 4038(1997)] are used to generate theoretical spectra for comparison with the experimental results taking lifetime vibration interference and Auger resonant Raman effects into account. Very good agreement is found for the lowest energy X ¹Σ⁺ final ionic state. Spectra of the higher energy final ionic states are decomposed into contributions from the different 5σ^-12π¹ and 1π^-12π¹ configurations for comparison of the calculated and experimental partial Auger decay rates. A revised value for the adiabatic ionization energy of the ¹Δ ionic state results from the deconvolution

[en] Here, we demonstrate that experiments measuring the transition energies of rare-earth ions doped in crystalline lattices are sensitive to violations of local Lorentz invariance and Einstein's equivalence principle. Using the crystal field of LaCl₃ as an example, we calculate the frame-dependent energy shifts of the transition frequencies between low-lying states of Ce³⁺, Nd³⁺, and Er³⁺ dopants in the context of the standard model extension, and show that they have high sensitivity to electron anomalies that break rotational invariance.

[en] Here, we investigate how single- and multi-vortex-ring states can emerge from a planar dark soliton in three-dimensional (3D) Bose-Einstein condensates (confined in isotropic or anisotropic traps) through bifurcations. We characterize such bifurcations quantitatively using a Galerkin-type approach and find good qualitative and quantitative agreement with our Bogoliubov–de Gennes (BdG) analysis. We also systematically characterize the BdG spectrum of the dark solitons, using perturbation theory, and obtain a quantitative match with our 3D BdG numerical calculations. We then turn our attention to the emergence of single- and multi-vortex-ring states. We systematically capture these as stationary states of the system and quantify their BdG spectra numerically. We found that although the vortex ring may be unstable when bifurcating, its instabilities weaken and may even eventually disappear for sufficiently large chemical potentials and suitable trap settings. For instance, we demonstrate the stability of the vortex ring for an isotropic trap in the large-chemical-potential regime.

[en] In this study, excitation energies, term designations, g factors, transition rates, and lifetimes of U²⁺ are determined using a relativistic configuration interaction (CI) + linearized-coupled-cluster (LCC) approach. The CI-LCC energies are compared with CI + many-body-perturbation-theory (MBPT) and available experimental energies. Close agreement has been found with experiment, within hundreds of cm^-1. In addition, lifetimes of higher levels have been calculated for comparison with three experimentally measured lifetimes, and close agreement has been found within the experimental error. CI-LCC calculations constitute a benchmark test of the CI + all-order method in complex relativistic systems such as actinides and their ions with many valence electrons. The theory yields many energy levels, g factors, transition rates, and lifetimes of U²⁺ that are not available from experiment. Lastly, the theory can be applied to other multivalence atoms and ions, which would be of interest to many applications.

[en] Here, we investigate the two-photon double ionization of beryllium atom induced by ultrashort pulses. We use a time-dependent formalism to evaluate the ionization amplitudes and generalized cross sections for the ejection of the 2s² valence shell electrons in the presence of a fully occupied 1s² frozen core shell. The relative contributions of the two-photon direct and sequential process are systematically explored by varying both pulse duration and central frequency. The energy and angular differential ionization yields reveal the signatures of both mechanisms, as well as the role of electron correlation in both the single and double ionization continua. In contrast with previous results on the helium atom, the presence of an electronic core strongly affects the final state leading to back-to-back electron emission even in the a priori less correlated two-photon sequential mechanism. In particular, a dominant pathway via excitation ionization through the Be⁺(2p) determines the profiles and pulse-duration dependencies of the energy and angle differential yields.

[en] The construction of high-fidelity control fields that are robust to control, system, and/or surrounding environment uncertainties is a crucial objective for quantum information processing. Using the two-state Landau-Zener model for illustrative simulations of a controlled qubit, we generate optimal controls for π/2 and π pulses and investigate their inherent robustness to uncertainty in the magnitude of the drift Hamiltonian. Next, we construct a quantum-control protocol to improve system-drift robustness by combining environment-decoupling pulse criteria and optimal control theory for unitary operations. By perturbatively expanding the unitary time-evolution operator for an open quantum system, previous analysis of environment-decoupling control pulses has calculated explicit control-field criteria to suppress environment-induced errors up to (but not including) third order from π/2 and π pulses. We systematically integrate this criteria with optimal control theory, incorporating an estimate of the uncertain parameter to produce improvements in gate fidelity and robustness, demonstrated via a numerical example based on double quantum dot qubits. For the qubit model used in this work, postfacto analysis of the resulting controls suggests that realistic control-field fluctuations and noise may contribute just as significantly to gate errors as system and environment fluctuations.

No abstract available

[en] We study the azimuthal asymmetry in the Drell-Yan lepton pair production in hadronic scattering processes at moderate transverse momentum region, taking into account the contributions from the twist-three quark-gluon correlations from the unpolarized hadrons. The contributions are found to dominate the asymmetry, and are not power suppressed by qt/Q at small qt where qt and Q are the transverse momentum and invariant mass of the lepton pair. Accordingly, the Lam-Tung relation will be violated at this momentum region, and its violation depends on the twist-three functions. However, at large transverse momentum qt ∼ Q, the Lam-Tung relation still holds because all corrections are power suppressed by Lambda2/qt2 ∼ Lambda2/Q2 where Lambda is the typical nonperturbative scale

[en] We present measurements of the absolute photoionization cross section of the aluminum like Si"+ ion over the 94-137 eV photon energy range. The measurements were performed using the merged-beam setup on the PLEIADES beamline at the SOLEIL synchrotron radiation facility. Signals produced in the Si"2"+ and Si"3"+ photoionization channels of the 2p subshell of the Si"+ ion from both the 1s"22s"22p"63s"23p"2 P_1_/_2_,_3_/_2 ground levels and the 1s"22s"22p"63s"3p"2 "4P metastable levels were observed. Absolute cross sections were determined. Calculations of the 2p inner-shell photoionization cross sections were carried out using the multiconfiguration Dirac-Fock and Dirac-Coulomb R-matrix theoretical approaches and are compared with experiment. (authors)

[en] Absolute photoionization cross-section measurements for a mixture of ground and metastable states of Xe4+, Xe5+, and Xe6+ are reported in the photon energy range of 4d->nf transitions, which occur within or adjacent to the 13.5 nm window for extreme ultraviolet lithography light source development. The reported values allow the quantification of opacity effects in xenon plasmas due to these 4d nf autoionizing states. The oscillator strengths for the 4d->4f and 4d->5f transitions in Xeq+ (q=1-6) ions are calculated using nonrelativistic Hartree-Fock and random phase approximations. These are compared with published experimental values for Xe+ to Xe3+ and with the values obtained from the present experimental cross-section measurements for Xe4+ to Xe6+. The calculations assisted in the determination of the metastable content in the ion beams for Xe5+ and Xe6+. The experiments were performed by merging a synchrotron photon beam generated by an undulator beamline of the Advanced Light Source with an ion beam produced by an electron cyclotron resonance ion source