Search

A Fourier-transform recording of protactinium in the infrared range is reanalysed with high precision in order to determine the hyperfine interaction constants A and B. Starting with a selection of best lines and least-squares fits of hyperfine structure intervals, large systems of linear equations compare experimental hyperfine peak wavenumbers with a theoretical representation. The theoretical representation is based on Ritz's combination principle and Casimir's formula according to the existing classification. Weighted least-squares fits allow a discrimination between unperturbed and perturbed data such as blended hyperfine structure components. For the first time, the wavenumbers of the hyperfine components of more than 600 lines are fitted using the characteristics of about 250 levels as parameters. When adding adjustable wavenumber-scale correction parameters, global consistency for the whole IR spectrum is obtained with local limits of about 0.3 × 10 - 3 cm - 1 . This demonstrates the high precision in both recording and analysis. The values of the fine structure energies are revised. Standard errors around 0.1 × 10 - 3 cm - 1 for the A constants and 10 - 3 cm - 1 for the B constants and the fine structure energies are achieved. Representative examples illustrate extensive results obtained for atomic protactinium. This high precision facilitates further search for new energy levels, and 20 new levels were presented. Foreword The data presented here are the results of a study carried out at the Laboratoire Aimé Cotton (LAC) at Paris-Orsay in the years 2003 and 2004, when I was there for a research stay. At this time, I worked together with Jean-François Wyart and Annie Ginibre on the re-examination of protactinium spectra that have been measured about 30 years earlier and that were available in the form of a printed list of peak wavenumbers and a printed paper chart of the intensity profile. The spectra had already been analysed, but there was still a lot of additional information that could be extracted from the spectra with time and effort. The review of the data, the selection of the data and the step-by-step optimization of the data set took a lot of time. When I returned to Berlin in 2004, we had made good progress, but in principle, it is like a bottomless pit. We continued together to optimize the data and tried to the finishing touches to it. At some point, we decided that we had reached a 'level of maturity' where the data could be published. We have discussed a lot about how detailed the text should be. This discussion has dragged on over the years and this project has repeatedly been lost in the stream of other everyday tasks. Every now and then there was a small attempt to return to this topic, but it quickly got lost in the daily hustle and bustle. In 2012, we presented the results at a conference. The death of both of them within two years hit me hard. I very much regret that this work was not published earlier. This special volume was the right motivation for me to finally publish this data. I no longer have access neither to the computer programs used at the time, which ran on large computer systems, nor to the original measurement data. I have not been able to find out what happened to the large quantity of paper (printed list of peak wavenumbers anda printed paper chart of spectra). But I have a bunch of input and output files of the calculations that have become a bit jumbled over the years, which contain a lot of information, as well as our unfinished manuscript. The resulting data contain important information for posterity – particularly since the element is radioactive and the experiments to collect laboratory data are unlikely to be repeated any time soon. I think it is worth publishing these data. High precision FT spectra of Pa: analysis of fine and hyperfine structure [ABSTRACT FROM AUTHOR]

The degree of linear polarization of the line x corresponding to the transition 1 s 2 p 3 P 2 → 1 s 2 1 S 0 is considered for Helium-like ions with non-zero nuclear spin. We are interested in this paper to seven ions: P 13 + , V 21 + , Mn 23 + , As 31 + , Rb 35 + , Y 35 + and Nb 39 + which are excited by electrons beam. In such ions, two kind of transitions occurs in the line x: the hyperfine-induced electric dipole E1 transition and the magnetic quadrupole M2 transition. From our results, we find that when we take into account this two kind of transitions without interference between the two channels E1 and M2, this leads to a drastic depolarization. However, the consideration of the interference effect leads to an increase in the polarization degree, slight for the whole line x and substantial for its individual hyperfine components. [ABSTRACT FROM AUTHOR]

In this paper, the thermodynamic properties of a rotating Bose gas in harmonic trap are investigated. In particularly, the condensate fraction, critical temperature and heat capacity are analytically calculated. A simple semiclassical approximation, which is the density of state approach, is suggested. This approach is able to include the effects, such as the finite size and the chemical potential when becomes equal to the energy of the lowest energy state, that altered the rotating ideal Bose gas simultaneously. The calculated results show that the thermodynamic properties depend strongly on the rotation rate. The rapid rotation leads to a highly anisotropic confinement potential. The possibility for dimensionality cross-over to lower dimensions for this system is discussed. We compare the outcome results with the experimental measured data of Coddington et al. [Phys. Rev. A 70, 063607 (2004)]. [ABSTRACT FROM AUTHOR]

In a recent paper, Verma et al. [Eur. Phys. J. D 42, 235 (2007)] have reported results for energy levels, radiative rates, collision strengths, and effective collision strengths for transitions among the lowest 17 levels of the (1s22s22p6)3s23p6, 3s23p53d and 3s3p63d configurations of Ni xi. They adopted the civ3 and R-matrix codes for the generation of wavefunctions and the scattering process, respectively. In this paper, through two independent calculations performed with the fully relativistic darc (along with grasp) and fac codes, we demonstrate that their results are unreliable. New data are presented and their accuracy is assessed. [ABSTRACT FROM AUTHOR]

Effects of vacuum polarization modify the energy levels in atoms with an orbiting particle heavier than an electron. The dominant effect is due to the Uehling potential. In this paper we consider the relativistic corrections to the energy levels caused by the Uehling potential and in particular the fine structure in muonic and antiprotonic atoms. We derive general expressions and consider in detail specific regions of parameters which allow simple asymptotic expansions. We take into account the recoil effects and anomalous magnetic moment in the case of an antiproton as the orbiting particle. [ABSTRACT FROM AUTHOR]

In this paper the treatment of a three-level atom which is confined in a Fabry-Perot optical cavity with a nonlinear mirror is investigated. Despite the nonlinear effects we show that this system operates in two different regimes. In one regime the system shows conventional laser properties which is approximated by a semiclassical laser theory and in the other one the system displays new quantum properties which is approximated by an effective two-level atom. For validity of the behavior of the system in two different regimes computer simulations are implemented. [ABSTRACT FROM AUTHOR]

In this paper, we present the study of the global classical dynamics of a rigid diatomic molecule in the presence of combined electrostatic and nonresonant polarized laser fields. In particular, we focus on the collinear field case, which is an integrable system because the z-component Pφ of the angular momentum is conserved. The study involves the complete analysis of the stability of the equilibrium points, their bifurcations and the evolution of the phase flow as a function of the field strengths and Pφ. Finally, the influence of the bifurcations on the orientation of the quantum states is studied. [ABSTRACT FROM AUTHOR]

In this paper we review the present status on heteronuclear trap loss rate (/3') for alkali mixtures held in a magneto-optical trap (Na-K, Na-Rb, Na-Cs, K-Rb, Rh-Cs, Li-Cs). The intensity dependence of the /3' for the mixture Cs-K is also presented for the first time in this report. The measurement techniques and a semiclassical model, considering both excited-ground and doubly excited channels, are reviewed. The comparison between the model and the experimental results indicates that radiative escape may be the dominant loss process for heteronuclear cold collisions. The obtained values for the crossed species trap loss indicate possibilities of future experiments involving such mixtures in a two species condensate. [ABSTRACT FROM AUTHOR]

The three-photon ionization in Ca from 482 1S0 ground state is studied. The two-photon process is a near resonance process with one of the following bound states: 4s4d 1D2, 4p2 3P2, 4s6s 1S0, 4p2 1D2 and 4p2 1S0 while the third photon reach either directly the continuum or one of the autoionizing states. The succession of bound states as well as the transitions above the ionization limit are discussed. The dynamics of the multiphoton excitation processes is also discussed and radiative decay of 4p2 1S0 Ca state with two-photon excitation as well as (the measured) decay times of the Ca autoionizing states using the proper line profiles for different quantum numbers has been determined. [ABSTRACT FROM AUTHOR]

We use the method that combines linearized coupled-cluster and configuration interaction approaches for calculating energy levels and multipole transition probabilities in singly ionized tin ions. We show that our calculated energies agree very well with the experimental data. We present probabilities of magnetic dipole and electric quadrupole transitions and use them for the analysis of the AT2017gfo kilonova emission spectra. This study demonstrates the importance and utility of accurate atomic data for forbidden transitions in the examination of future kilonova events. [ABSTRACT FROM AUTHOR]

We study the general (2+1)-dimensional Davey-Stewartson (DS) equations with nonlinear and gain terms and acquire explicit solutions through variable separation approach. In particular, we deduce some main novel excitations for the DS equations, and further demonstrate different features of these excitations. More importantly, the similar solutions and excitations can be predicted to exist in other related revolution equations such as nonlinear Schrödinger equation to explain the Bose-Einstein condensation. [ABSTRACT FROM AUTHOR]

A Rydberg atom embedded in a plasma can experience penetration by slowly moving electrons within its volume. The original pure Coulomb potential must now be replaced by a screened Coulomb potential which contains either a screening length Rs or a screening factor A = Rs -1 . For any given discrete energy level, there is a Critical Screening Factor (CSF) Ac beyond which the energy level disappears (by merging into the continuum). Analytical results are obtained for the classical dependence of the energy on the screening factor, for the CSF, and for the critical radius of the electron orbit for Circular Rydberg States (CRS) in this screened Rydberg atom. The results are derived for any general form of the screened Coulomb potential and are applied to the particular case of the Debye potential. We also show that CRS can temporarily exist above the ionization threshold and are therefore the classical counterparts of quantal discrete states embedded into continuum. The results are significant not only to Rydberg plasmas, but also to fusion plasmas, where Rydberg states of multi-charged hydrogen-like ions result from charge exchange with hydrogen or deuterium atoms, as well as to dusty/complex plasmas. [ABSTRACT FROM AUTHOR]

Dispersed fluorescence from fragments formed after the de-excitation of the 1s-1π* resonances of N*O and NO* has been measured in the spectral range of 118–142 nm. This range is dominated by lines of atomic nitrogen and oxygen fragments and by the $A ~^{1}{\rm \Pi} \left(v^{\prime}\right) \rightarrow X ~^{1}{\rm \Sigma}^{+}\left(v^{\prime \prime}\right)$ bands in the NO+ ion which result from the participator Auger decay of the 1s-1π* resonances. Ab-initio calculations of the transition probabilities between vibrational levels during the reaction NO $X~^{2}{\rm \Pi}\left(v_{0}=0\right) \rightarrow $ N*O $\left( {\rm NO}^{\ast}\right) $ $1s^{-1}\pi ^{\ast }\left( v_{r}\right) $ ⇒ NO $^{+}~A~^{1}{\rm \Pi} \left(v^{\prime}\right) \rightarrow X~^{1}{\rm \Sigma}^{+}\left(v^{\prime \prime}\right)$ were used to explain the observed intensity dependence for the $A\left(v^{\prime }\right) \rightarrow X\left(v^{\prime \prime}\right)$ fluorescence bands on the exciting-photon energy across the resonances and on both v′ and v′′ vibrational quantum numbers. The multiplet structure of the 1s-1π* resonance and lifetime vibrational interference explain the observed exciting-photon energy dependence of the $A\left( v^{\prime}\right) \rightarrow X\left(v^{\prime \prime}\right)$ fluorescence intensity. A strong spin-orbit coupling between singlet and triplet states of NO+ is proposed to reduce additional cascade population of the $A~^{1}{\rm \Pi}$ state via radiative transitions from the $W~^{1}{\rm \Delta}$ and $A^{\prime}~^{1}{\rm \Sigma}^{-}$ states and to explain remaining differences between measured and calculated integral fluorescence intensities. [ABSTRACT FROM AUTHOR]

For both cases with and without interactions, bipartite entanglement of two fermions from a Fermi gas in a trap is investigated. We show how the entanglement depends on the locations of the two fermions and the total particle number of the Fermi gas. Fermions at the edge of trap have longer entanglement distance (beyond it, the entanglement disappears) than those in the center. We derive a lower limitation to the average overlapping for two entangled fermions in the BCS ground state, it is shown to be $\sqrt{Q/2M}$ , a function of Cooper pair number Q and the total number of occupied energy levels M. [ABSTRACT FROM AUTHOR]

The one-electron quantum-electrodynamic corrections to the magnetic-dipole transition amplitude between the fine-structure levels (1s2 2s2 2p) 2P3/2 - 2P1/2 in boronlike ions are calculated to all orders in αZ. The results obtained serve for improving the theoretical accuracy of the lifetime of the (1s2 2s2 2p) 2P3/2 level in boronlike argon. [ABSTRACT FROM AUTHOR]

ab initio calculations of dielectronic recombination rate coefficient of W 37 + forming W 36 + and electron-impact ionization cross section of W 36 + have been performed. Energy levels, radiative transition probabilities, autoionization rates, electron-impact excitation and ionization cross sections are calculated using the flexible atomic code (FAC). Good agreement between the present level-to-level distorted wave treatment and previous ADAS data is found for the dielectronic recombination rate coefficients of W 37 + . Electron-impact direct ionization and excitation-autoionization contributions to the total single-ionization cross sections were calculated employing a level-to-level distorted-wave approximation. The calculation result shows that the total ionization cross section will be underestimated by 50% near ionization threshold to ∼ 8% at higher energy without include the contribution from excitation-autoionization process. [ABSTRACT FROM AUTHOR]

The energies of the levels belonging to a Rydberg series 1snp 1,3 3P in a two electron atom have been determined by means of the quantum defect theory for a two-electron atom with nuclear charge Z considered as a parameter. Comparison with configuration interaction calculations suggests that the analytic quantum defect expression for the energy levels may be in fact asymptotically exact as Z ↠1, providing an analytic description of the disappearance of the Rydberg states with L > 0 when Z approaches the value of 1. [ABSTRACT FROM AUTHOR]

Considering the quantum effects of diffraction and the collective screening effects, the potential of test charge in semiclassical plasmas is derived. It is generalized exponential screened Coulomb potential. Using the Ritz variational method incorporating this potential, the effects of semiclassical plasma on the energy levels and radiative transitions are investigated systematically, taking highly charged H-like ion as an example. The Debye plasma model is also employed for comparison purposes. Comparisons and analysis are made between these two sets of results and the differences are discussed. Graphical abstract: [ABSTRACT FROM AUTHOR]

We present 39 even and 60 odd parity newly discovered fine structure levels of Pr I with angular momentum quantum numbers J = 7 / 2, 9/2, 11/2 and 13/2. Spectral lines in the wavelength range of 4200 Å to 7500 Å were investigated experimentally using laser-induced fluorescence spectroscopy or optogalvanic spectroscopy. Free Pr atoms were produced in a hollow cathode discharge. A high resolution Fourier transform spectrum of Pr was used to extract excitation wavelengths. From an analysis of the recorded hyperfine patterns, together with excitation and fluorescence wavelengths, we were able to find the unknown levels involved in the formation of the investigated lines. More than 500 spectral lines could be classified by the new levels. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The propagation of a probe laser field in a cavity optomechanical system with a Bose-Einstein condensate is studied. The transmission properties of the system are investigated and it is shown that the group velocity of the probe pulse field can be controlled by Rabi frequency of the pump laser field. The effect of the decay rate of the cavity photons on the group velocity is studied and it is demonstrated that for small values of the decay rates, the light propagation switches from subluminal to superluminal just by changing the Rabi frequency of the pump field. Then, the gain-assisted superluminal light propagation due to the cross-Kerr nonlinearity is established in cavity optomechanical system with a Bose-Einstein condensate. Such behavior can not appear in the pump-probe two-level atomic systems in the normal phase. We also find that the amplification is achieved without inversion in the population of the quantum energy levels. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Plasma screening effects on the energy structure and radiative transition properties of helium-like C ions embedded in Debye plasmas are investigated by using the multi-configuration Dirac-Hartree-Fock method incorporating the Debye-Hückel potential for both the electron-nucleus and electron-electron interactions. Seventeen fine-structure energy levels of the low-lying 1 s, 1 s2 l( l = s,p) and 1 s3 l′( l′ = s,p,d) configurations, as well as the electric-dipole ( E1), magnetic-dipole ( M1) and magnetic-quadrupole ( M2) transition probabilities and oscillator strengths between these levels have been calculated over a wide range of screening parameters. It is found that the plasma screening leads to a decrease of excitation energies and alters the energy levels remarkably. For Δn ≠ 0 transitions, the spontaneous decay spectra are red-shifted and their oscillator strengths and transition probabilities decrease with increasing the interaction screening, while those for the Δn = 0 transitions exhibit opposite patterns. The influence of electron-nucleus and electron-electron screened interactions on the changes of energy levels and transition properties are analyzed. Comparison is made of present results with other data available in the literature for this ion. [ABSTRACT FROM AUTHOR]

The cross sections for rotational, fine-structure and projection-change transitions in collision of MgH (Σ) molecule with He and He atoms were computed at cold and ultracold temperatures using the ab initio potential energy surface. The significant suppression feature and resonance pattern caused by spin-rotation interaction were found and discussed. The collisions exhibit a strong isotope effect in the ultracold regime. The rotational relaxations of the fine-structure excited energy levels tendentiously preserve the F index. The ratio of the cross sections for elastic and spin-flipping collision with He partner is always greater than seven orders of magnitude for the energy range 10−1cm and suggests the MgH molecule is a good candidate for He buffer gas cooling. [ABSTRACT FROM AUTHOR]

Energy levels, Auger decay and radiative transition rates of the doubly-excited 1 s3 l3 l′ states for Be-like neon are calculated using relativistic Multiconfiguration Dirac-Fock (MCDF) method. Electron correlation and relaxation effects are taken into account. The magnitude of Auger rates for the 35 doubly-excited states and their decay channels are discussed. Present calculated values are in agreement with the latest experimental electron spectra as well as other theoretical results. [ABSTRACT FROM AUTHOR]

For the study of the nature of binding in the Sc dimer, the ground state, XΣ, was calculated by the valence multireference configuration interaction method with single and double excitations plus Davidson correction, MRCISD (+Q), at the complete basis set (CBS) limit. The employment of the C symmetry group, allowed us to obtain the Sc atoms in different states at the dissociation limit. From the Mulliken population analysis and comparison with atomic energies follows that in the ground state Sc dissociates on one Sc in the ground state and the other in the second excited quartet state, F. The spectroscopic parameters of the ground potential curve, obtained at the valence MRCISD (+Q)/CBS level, are: R = 5.20 bohr, D = 50.37 kcal/mol, and ω = 234.5 cm. The obtained value for the harmonic frequency agrees very well with the experimental one, ω = 239.9 cm. The dissociation energy with reference to the dissociation on two Sc in the ground states was estimated as D = 9.98 kcal/mol. In contrast with many other studied transition-metal dimers, which are attributed to the van der Waals bonded molecules, the Sc dimer is stabilized by the covalent bonding on the hybrid atomic orbitals. [ABSTRACT FROM AUTHOR]

We provide a new class of entanglement witnesses for d ⊗ d systems (two qudits). Our construction generalizes the one proposed recently by Jafarizadeh et al. for d = 3 and d = 4 on the basis of semidefinite linear programming. Moreover, we provide a new class of PPT entangled states detected by our witnesses which generalizes well known family of states constructed by Horodecki et al. for d = 3. [ABSTRACT FROM AUTHOR]

The entanglement dynamics of three-qubit states under an XY spin chain at finite temperature with three-site interaction is investigated. It is shown that the three-site interaction does not affect the behavior of quantum phase transition (QPT) induced by the external magnetic field and does not induce new critical regions in the XY model. In addition, concerned with the effect of the three-site interaction on the entanglement evolution, we find the three-site interaction can not only enhance but also suppress the decay of the entanglement between the three-qubit system, which depends on the initial states of the system and the parameters related with the environmental spin chain. [ABSTRACT FROM AUTHOR]

We examine the theoretical limits of the generation of entanglement in a damped coupled ion-cavity system using jump-based feedback. Using Raman transitions to produce entanglement between ground states reduces the necessary feedback bandwidth, but does not improve the overall effect of the spontaneous emission on the final entanglement. We find that the fidelity of the resulting entanglement will be limited by the asymmetries produced by vibrations in the trap, but that the concurrence remains above 0.88 for realistic ion trap sizes. [ABSTRACT FROM AUTHOR]

We propose a linear optical protocol for teleporting a multi( W)-photon Greenberger-Horne-Zeilinger (GHZ) polarization-entangled state from a sender to a receiver under control of a number of controllers in terms of optical elements. We show that the protocol can be successfully realized with a certain probability. This protocol has the advantage of transmitting much less particles and classical information for teleporting the W-photon GHZ polarization-state than others, and the protocol is based on linear optical elements and postselection strategy, which are feasible with existing experimental technology. [ABSTRACT FROM AUTHOR]

The interaction between a superconducting phase qubit and the two-level systems located inside the Josephson tunnel barrier is described by the XY model, which is naturally used to implement the i-SWAP gate. With this gate, we propose a scheme to efficiently generate multi-qubit entangled states of such two-level systems, including multipartite W state and cluster states. In particular, it is found that, with the help of the phase qubit, the entanglement witness can be used to efficiently detect the produced multi-qubit entangled states. [ABSTRACT FROM AUTHOR]

We investigate the entanglement properties of symmetry states of the Schur-Weyl duality. Our approach based on reduced two-qubit density matrices, and concurrence as the measure of entanglement. We show that all kinds of 'entangled graphs", which describe the entanglement structure in Schur-Weyl states are completely coded in the corresponding Young tableau. [ABSTRACT FROM AUTHOR]

The sum rule for the transition rates between the components of two multiplets, known for the one-photon transitions, is extended to the multiphoton transitions in hydrogen and hydrogen-like ions. As an example the transitions 3p- 2p, 4p- 3p and 4d- 3d are considered. The numerical results are compared with previous calculations. [ABSTRACT FROM AUTHOR]

In the framework of the U ( su(2)) quantum algebra, we investigate the entanglement properties of two-spin systems, of arbitrary spins j and j, defined in an entanglement of deformed spin coherent states of each of the spins. We derive the amount of entanglement and we give conditions under which bipartite entangled states become maximally entangled. Using these conditions, we construct a large class of Bell states for any choices of the parameters that specify the spin coherent states. [ABSTRACT FROM AUTHOR]

We demonstrate that the idea of quantum control can be generalized to construct the exact many-body coherent state (MBCS) in a trapped Bose-Einstein condensate (BEC) of N atoms. Such a MBCS possesses the form of the single-particle coherent state, which does not deform in propagation and is stable for a repulsive BEC. The results suggest an experimental scheme for resonantly generating and coherently controlling the MBCSs. [ABSTRACT FROM AUTHOR]

three photon resonance arising due to coherent population trapped (CPT) states in multi-level systems, is experimentally shown to be a powerful spectral marker to detect interacting CPT states. In systems showing N type or double Λ type level configurations, these absorption resonances can be used to identify spectral positions of maximal interactions between competing CPT ground states. The contrast of the absorption resonance serves to identify even partially destructive interactions between the CPT states, eliminating the need for strong resonant changes of ground state coherence for identification. We demonstrate this effect in a room temperature, gaseous collection of Rb. atoms. Three laser fields interact with a double Λ configuration in the Zeeman degenerate levels of the ground state 5 $S_{1/2}$, F = 1 and those of the excited states 5 $P_{3/2}$, F = 0,1, around the D2 line. The three-photon resonance is studied in the counter-propagating third field when the other two co-propagating fields satisfy the two-photon resonance condition necessary for creation of CPT states. We envisage that this absorption feature in the third field, can become a veritable tool to quantify degradation of CPT induced effects in engineered quantum states using multi-level systems. [ABSTRACT FROM AUTHOR]

The electron affinity of tungsten has been measured using laser photodetachment threshold spectroscopy in a collinear geometry. The electron affinity was determined to 6583.6(6) cm by observing the onset of the process when W ions in the $5d^56s^2$S ground state are photodetached producing neutral W atoms in the $5d^46s^2$D ground state. The measured value is in agreement with previous measurements and improves the accuracy by almost two orders of magnitude. Further, a photodetachment signal below the ground state photodetachment threshold was found, which indicates the existence of a bound excited state in W. [ABSTRACT FROM AUTHOR]

We theoretically analyze the entanglement generation and dynamics by coupled Josephson junction qubits. Considering a current-biased Josephson junction (CBJJ), we generate maximally entangled states. In particular, the entanglement dynamics is considered as a function of the decoherence parameters, such as the temperature, the ratio r ≡ $\omega_c$/ $\omega_0$ between the reservoir cutoff frequency $\omega_c$ and the system oscillator frequency $\omega_0$, and the energy levels split of the superconducting circuits in the non-Markovian master equation. We analyzed the entanglement sudden death (ESD) and entanglement sudden birth (ESB) by the non-Markovian master equation. Furthermore, we find that the larger the ratio r and the thermal energy k BT, the shorter the decoherence. In this superconducting qubit system we find that the entanglement can be controlled and the ESD time can be prolonged by adjusting the temperature and the superconducting phases $\Phi_k$ which split the energy levels. [ABSTRACT FROM AUTHOR]

We investigate the entanglement properties of bound states in an exactly soluble two-electron model, the Moshinsky atom. We present exact entanglement calculations for the ground, first and second excited states of the system. We find that these states become more entangled when the relative inter-particle interaction becomes stronger. As a general trend, we also observe that the entanglement of the eigenstates tends to increase with the states’ energy. There are, however, “entanglement level-crossings” where the entanglement of a state becomes larger than the entanglement of other states with higher energy. In the limit of weak interaction, we also compute (exactly) the entanglement of higher excited states. Excited states with anti-parallel spins are found to involve a considerable amount of entanglement even for an arbitrarily weak (but non zero) interaction. This minimum amount of entanglement increases monotonically with the state’s energy. Finally, the connection between entanglement and the Hartree-Fock approximation in the Moshinsky model is addressed. The quality of the ground-state Hartree-Fock approximation is shown to deteriorate, and the corresponding correlation energy to grow, as the entanglement of the (exact) ground state increases. The present work goes beyond previous related studies because we fully take into account the identical character of the two constituting particles in the entanglement calculations, and provide analytical, exact results both for the ground and the first few excited states. [ABSTRACT FROM AUTHOR]

A B-spline-based configuration interaction method is used to compute the energy levels of the ground and a few excited states of heliumlike atoms confined in a finite external square-well potential, as a function of the depth of the confining shell potential. The electron probability density and the dependence of the energy levels in the shell potential are used to account for the electron-electron interaction when the atoms are submitted to such an environment. [ABSTRACT FROM AUTHOR]

We studied the relaxation of hollow atoms by two-photon transitions during the stopping of slow (E=8.5q keV) highly charged Pbq+ (q=53–58) ions in a thin Ta foil. The X-rays emitted during the relaxation process were detected in coincidence with two Si(Li) detectors. Particular attention was paid to the role of the internal dielectronic excitation (IDE) in the relaxation dynamics. We found a clear contribution to relaxation by the IDE process also for projectiles with initial M-shell vacancies and IDE speeds up relaxation of electrons from high Rydberg states by directly filling vacancies in the N-shell that is accompanied with the excitation of M-shell electrons. We discuss the relaxation mechanism, and present results for the fluorescence yield and the IDE probability of highly charged Pb ions in a solid. [ABSTRACT FROM AUTHOR]

We propose a scheme for the generation of an arbitrary quantum states for multiple trapped ions in the symmetric Dicke subspace. One can manipulate the collective ion transition in a selective symmetric Dicke subspace via the virtual excitation induced inequidistant energy levels. All the states undergo the same phonon-number-dependent Stark shift and thus the scheme is insensitive to the thermal motion. Furthermore, the scheme does not require individual addressing of the ions. [ABSTRACT FROM AUTHOR]

A method is presented to calculate the radiative transition probabilities and the radiative recombination rate coefficients between electronic molecular states. Total transition probabilities are determined from vibrational transition probabilities without considering the detailed rotational structure of the molecular electronic states. Radiative recombination rate coefficients are obtained from the computation of vibrational photo-ionisation cross sections. Concerning spontaneous emission, Lyman (B → X) and Werner (C → X) band systems of H2 and Meinel (A → X), (B → A) and (B → X) band systems of OH are investigated. For radiative recombination, transitions between H (X) and H2(X), and between OH+(X, a, A, b, and c) and OH(X) are considered. Transition probabilities and recombination rate coefficients are calculated as a function of temperature in the range 1500–15 000 K. [ABSTRACT FROM AUTHOR]

We report on a high resolution study of two excited electronic states of the LiCs molecule, namely the B1Π and the D1Π. The experimental data are derived from the Fourier transform spectroscopy on the ground states X1Σ+ and a3Σ+ [Phys. Rev. A 75, 042513 (2007)]. Along with the laser induced fluorescence also collisionally induced satellites are observed, which expand the data sets for the B1Π and D1Π states. The lower state, B1Π, is found to be free of significant local perturbations, although a strong dependence of the Λ-doubling on the vibrational and the rotational quantum numbers indicates a noticeable influence of the nearby 1Σ+ states. A set of Dunham coefficients and a potential energy curve for this state are derived. In contrast, the energy levels of both the e and f parities of the D1Π state were found to be strongly perturbed, making a precise description within a single channel model impossible. Nevertheless we present an approximated experimental potential energy curve which can be applied in a further deperturbation analysis. We discuss the prospects of these electronic states for the formation of cold LiCs molecules in a magneto-optical trap of mixed species. [ABSTRACT FROM AUTHOR]

We present a theoretical study of bose condensation of non-interacting bosons in finite lattices in quartic potentials in one, two, and three dimensions. We investigate dimensionality effects and quartic potential effects on single boson density of energy states, condensation temperature, condensate fraction, and specific heat. The results obtained are compared with corresponding results for lattice bosons in harmonic traps. [ABSTRACT FROM AUTHOR]

Excitation energies from ground state for 86 fine-structure levels as well as oscillator strengths and radiative decay rates for all fine-structure transitions among the levels of the terms (1s22s22p6)3s2(1S), 3s3p(1,3Po), 3s3d(1,3D), 3s4s(1,3S), 3s4p(1,3Po), 3s4d(1,3D), 3s4f(1,3Fo), 3p2(1S, 3P, 1D), 3p3d(1,3Po, 1,3Do, 1,3Fo), 3p4s(1,3Po), 3p4p(1,3S, 1,3P, 1,3D), 3p4d(1,3Po, 1,3Do, 1,3Fo), 3p4f(1,3D, 1,3F, 1,3G) and 3d2(1S, 3P, 1D, 3F,1G) of Cr XIII are calculated using extensive configuration-interaction (CI) wave functions obtained with the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are included through the Breit-Pauli approximation via spin-orbit, spin-other-orbit, spin-spin, Darwin and mass correction terms. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made. The mixing among several fine-structure levels is found to be very strong. Our excitation energies, including their ordering, are in excellent agreement (better than 0.5%) with the available experimental results. From our transition probabilities, we have also calculated radiative lifetimes of some fine-structure levels. Our calculated lifetime for the longer-lived level 3s3p(3P1) is found to be in excellent agreement with the experimental result of Curtis compared to other theoretical calculations. [ABSTRACT FROM AUTHOR]

We discuss the effects of experimental resolution on the analysis of nearest neighbour energy level spacings for the signatures of underlying classically chaotic electron dynamics. Through a numerical treatment we arrive at a new dimensionless resolution criterion which must be met in order that statistical studies of this kind be considered meaningful. [ABSTRACT FROM AUTHOR]

We present a theoretical study of Bose condensation and specific heat of non-interacting bosons in finite lattices in harmonic potentials in one, two, and three dimensions. We numerically diagonalize the Hamiltonian to obtain the energy levels of the systems. Using the energy levels thus obtained, we investigate the temperature dependence, dimensionality effects, lattice size dependence, and evolution to the bulk limit of the condensate fraction and the specific heat. Some preliminary results on the specific heat of fermions in optical lattices are also presented. The results obtained are contextualized within the current experimental and theoretical scenario. [ABSTRACT FROM AUTHOR]

Using variational and numerical solutions we show that stationary negative-energy localized (normalizable) bound states can appear in the three-dimensional nonlinear Schrödinger equation with a finite square-well potential for a range of nonlinearity parameters. Below a critical attractive nonlinearity, the system becomes unstable and experiences collapse. Above a limiting repulsive nonlinearity, the system becomes highly repulsive and cannot be bound. The system also allows nonnormalizable states of infinite norm at positive energies in the continuum. The normalizable negative-energy bound states could be created in BECs and studied in the laboratory with present knowhow. [ABSTRACT FROM AUTHOR]

For two discrete-level quantum systems in interaction, we follow the displacement in the complex plane of the eigen-energies of the compound system when the excited level of one of the two systems is enlarged. These new points are usually called resonances and describe mixed unstable states. This allows us to define and to calculate a critical value of the coupling constant which separates two well-known coupling regimes. These two regimes are thus described in a unified way. In the study, resonances which are usually not taken into account occur. They are studied in the large continuum case provided by the coupling of the hydrogen atom to the states of the transverse electromagnetic field in the vacuum. We justify that some of these resonances be neglected in this case. [ABSTRACT FROM AUTHOR]

The minimal energy configurations of finite Nv-body vortices in a rotating trapped Bose-Einstein condensate is studied analytically by extending the previous work [Y. Castin, R. Dum, Eur. Phys. J. D 7, 399 (1999)], and taking into account the finite size effects on z-direction and the bending of finite vortex lines. The calculation of the energy of the vortices as a function of the rotation frequency of the trap gives number, curvature, configuration of vortices and width of vortex cores self-consistently. The numerical results show that (1) the simplest regular polynomial of the several vortex configurations is energetically favored; while the hexagonal vortex lattice is more stable than square lattice; (2) bending is more stable then straight vortex line along the z-axis for λ<1; (3) the boundary effect is obvious: compared with the estimation made under infinite boundary, the finite size effect leads to a lower vortex density, while the adding vortex bending results in a less higher density because of the expansion. The results are in well agreement with the other authors' ones. [ABSTRACT FROM AUTHOR]

Laser spectroscopy with either optogalvanic or laser induced fluorescence detection have been employed to measure the hyperfine structure of 25 transitions of atomic niobium in the visible and near infrared spectral range. The magnetic dipole hyperfine interaction constants A of 43 energy levels (22 of even and 21 of odd parity) were determined, 30 of which have been investigated for the first time. The values obtained for the even parity levels are compared with the results of a parametric analysis. [ABSTRACT FROM AUTHOR]