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We present an updated value of the Muonium 1S–2S transition frequency, highlighting contributions from different QED corrections as well as the large uncertainty in the Dirac contribution, stemming from the uncertainty of the electron to muon mass ratio. Improving the measurement of this spectral line would allow to extract a more accurate determination of fundamental constants, such as the electron to muon mass ratio or, combined with the Muonium hyperfine splitting, an independent value of the Rydberg constant. Furthermore, we report on the current status of the Mu-MASS experiment, which aims at measuring the Muonium 1S–2S transition frequency at a 10kHz uncertainty level., The European Physical Journal D, 77 (4), ISSN:1434-6060, ISSN:1434-6079

We study the 1S-3S two-photon transition of hydrogen in a thermal atomic beam, using a homemade cw laser source at 205 nm. The experimental method is described, leading in 2017 to the measurement of the 1S-3S transition frequency in hydrogen atom with a relative uncertainty of $9 \times 10^{-13}$. This result contributes to the "proton puzzle" resolution but is in disagreement with the ones of some others experiments. We have recently improved our setup with the aim of carrying out the same measurement in deuterium. With the improved detection system, we have observed a broadened fluorescence signal, superimposed on the narrow signal studied so far, and due to the stray accumulation of atoms in the vacuum chamber. The possible resulting systematic effect is discussed.

This paper provides an explanation of the key effects behind the deflection of ultra-relativistic electron beams by means of oriented quasi-mosaic Bent Crystals (qmBC). It is demonstrated that accounting for specific geometry of the qmBC and its orientation with respect to a collimated electron beam, its size and emittance is essential for an accurate quantitative description of experimental results on the beam deflection by such crystals. In an exemplary case study a detailed analysis of the recent experiment at the SLAC facility is presented. The methodology developed has enabled to understand the peculiarities in the measured distributions of the deflected electrons. This achievement constitutes an important progress in the efforts towards the practical realization of novel gamma-ray crystal-based light sources and puts new challenges for the theory and experiment in this research area., Comment: 6 pages, 4 figures plus Supplemental Material

Brilliance of novel gamma-ray Crystal-based Light Sources (CLS) that can be constructed through exposure of oriented crystals to beams of ultra-relativistic charged particles is calculated basing on the atomistic scale numerical modeling of the channeling process. In an exemplary case study, the brilliance of radiation emitted in a diamond-based Crystalline Undulator LS by a 10 GeV positron beam available at present at the SLAC facility is computed. Intesity of CU radiation in the photon energy range 10^0 - 10^1 MeV, which is inaccessible to conventional synchrotrons, undulators and XFELs, greatly exceeds that of laser-Compton scattering LSs and can be higher than predicted in the Gamma Factory proposal to CERN. Construction of novel CLSs is a challenging task which constitutes a highly interdisciplinary field entangling a broad range of correlated activities. CLSs provide a low-cost altenative to conventional LSs and have enomorous number of applications., Comment: 6 pages, 4 figures plus Supplementary Material with 2 figures

We provide a brief review of how phase space techniques are explored within strong-field and attosecond science. This includes a broad overview of the existing landscape, with focus on strong-field ionisation and rescattering, high-order harmonic generation, stabilisation and free-electron lasers. Furthermore, using our work on the subject, which deals with ionisation dynamics in atoms and diatomic molecules as well as high-order harmonic generation in inhomogeneous fields, we exemplify how such tools can be employed. One may for instance determine qualitatively different phase space dynamics, explore how bifurcations influence ionisation and high-harmonic generation, establish for which regimes classical and quantum correspondence works or fails, and what role different time scales play. Finally, we conclude the review highlighting the importance of the tools available in quantum optics, quantum information and physical chemistry to strong-field laser-matter interaction., Comment: 38 pages, 12 figures, submitted to EPJ D

We propose a new scheme for an improved determination of the Newtonian gravitational constant G and evaluate it by numerical simulations. Cold atoms in free fall are probed by atom interferometry measurements to characterize the gravitational field generated by external source masses. Two source mass configurations having different geometry and using different materials are compared to identify an optimized experimental setup for the G measurement. The effects of the magnetic fields used to manipulate the atoms and to control the interferometer phase are also characterized.

The perceived dichotomy between analytical and ab initio approaches to theory in attosecond science is often seen as a source of tension and misconceptions. This Topical Review compiles the discussions held during a round-table panel at the 'Quantum Battles in Attoscience' CECAM virtual workshop, to explore the sources of tension and attempt to dispel them. We survey the main theoretical tools of attoscience -- covering both analytical and numerical methods -- and we examine common misconceptions, including the relationship between ab initio approaches and the broader numerical methods, as well as the role of numerical methods in 'analytical' techniques. We also evaluate the relative advantages and disadvantages of analytical as well as numerical and ab initio methods, together with their role in scientific discovery, told through the case studies of two representative attosecond processes: non-sequential double ionisation and resonant high-harmonic generation. We present the discussion in the form of a dialogue between two hypothetical theoreticians, a numericist and an analytician, who introduce and challenge the broader opinions expressed in the attoscience community., Comment: Proceedings of the round-table panel discussion 'Quantum Battle 3 - Numerical vs Analytical Methods' at the Quantum Battles in Attoscience online conference (https://www.quantumbattles.com/), the livestream for which can be found at https://www.youtube.com/watch?v=VJnFfHVDym4

The high-order harmonic generation in finite topological nanoribbons is investigated using a tight-binding description. The ribbons consist of hexagons and are almost one-dimensional. Two edge states emerge at the short edges of the ribbon after a gap closure between valence and conduction band, indicating a topological phase transition. The energies of those edge states as functions of the tight-binding parameters display crossings and avoided crossings, which influence the high-harmonic spectra., Comment: 8 pages, 7 figures

The present work studies aspects of the electronic correlation in confined H$^{-}$, He and Li$^+$ atoms in their ground states using the informational entropies. In this way, different variational wavefunctions are employed in order of better take account of Coulomb correlation. The obtained values for the $S_r$, $S_p$ and $S_t$ entropies are sensitive in relation to Coulomb correlation effects. In the strong confinement regime, the effects of the Coulomb correlation are negligible and the employment of the models of independent particle and two non-interacting electrons confined by a impenetrable spherical cage gains importance in this regime. Lastly, energy values are obtained in good agreement with the results available in the literature., Version accepted for publication in European Physical Journal D

Ground and excited states of a confined negative Hydrogen ion has been pursued under Kohn-Sham density functional approach by invoking a physically motivated work-function-based exchange potential. The exchange-only results are of near Hartree-Fock quality. Local parameterised Wigner-type, and gradient- and Laplacian-dependent non-local Lee-Yang-Parr functionals are chosen to investigate the electron correlation effects. Eigenfunctions and eigenvalues are extracted by using a generalized pseudospectral method obeying Dirichlet boundary condition. Energy values are reported for 1s$^{2}$ ($^{1}$S), 1s2s ($^{3,1}$S) and 1s2p ($^{3,1}$P) states. Performance of the correlation functionals in the context of confinement is examined critically. The present results are in excellent agreement with available literature. Additionally, Shannon entropy and Onicescu energy are offered for ground and low lying singly excited 1s2s ($^{3}$S) and 1s2p ($^{3}$P) states. The influence of electron correlation is more predominant in the weaker confinement limit and it decays with an increase in confinement strength. In essence, energy and some information measures are estimated using a newly formulated density functional strategy., Comment: 25 pages, 6 figures, 8 tables

Antihydrogen atoms are produced at CERN in highly excited Rydberg states. However, precision measurements require anti-atoms in ground state. Whereas experiments currently rely on spontaneous emission only, simulations have shown that THz light can be used to stimulate the decay towards ground state and thus increase the number of anti-atoms available for measurements. We review different possibilities at hand to generate light in the THz range required for the purpose of stimulated deexcitation. We demonstrate the effect of a blackbody type light source, which however presents drawbacks for this application including strong photoionization. Further, we report on the first THz transitions in a beam of Rydberg caesium atoms induced by photomixers and conclude with the implications of the results for the antihydrogen case.[graphic not available: see fulltext][graphic not available: see fulltext] Antihydrogen atoms are produced at CERN in highly excited Rydberg states. However, precision measurements require anti-atoms in ground state. Whereas experiments currently rely on spontaneous emission only, simulations have shown that THz light can be used to stimulate the decay towards ground state and thus increase the number of anti-atoms available for measurements. We review different possibilities at hand to generate light in the THz range required for the purpose of stimulated deexcitation. We demonstrate the effect of a blackbody type light source, which however presents drawbacks for this application including strong photoionization. Further, we report on the first THz transitions in a beam of Rydberg caesium atoms induced by photomixers and conclude with the implications of the results for the antihydrogen case.

We propose a method for transferring atoms to a target quantum state for a multilevel quantum system with sequentially increasing, but otherwise unknown, energy splitting. This is achieved with a feedback algorithm that processes off-resonant optical measurements of state populations during adiabatic rapid passage in real-time. Specifically, we reliably perform the transfer $|F=2,m_F=2\rangle \rightarrow |1,1\rangle \rightarrow |2,1\rangle$ for a sample of ultracold $^{87}$Rb in the presence of a random external magnetic field.

We revisit the pointer-based measurement concept of von Neumann which allows us to model a quantum counterpart of the classical time-of-flight (ToF) momentum. Our approach is based on the Hamiltonian for a particle interacting with two quantum pointers serving as basic measurement devices. The corresponding dynamics leads to a pointer-based ToF observable for the operational momentum of the particle. We can consider single measurements of our quantum pointers and show that this process will result in a state reduction for a single particle being downstream of the time-of-flight setup., 8 pages, 4 figures

Stability of the bound ground states in the six five-body muonic $a b \mu e_2$ ions (or $(a b \mu e_2)^{-}$) and ten six-body $a b c \mu e_2$ quasi-molecules is investigated. The notations $a, b, c$ stand for the bare nuclei of three hydrogen isotopes - protium ($p$), deuterium ($d$) and tritium ($t$). All these systems are the Coulomb five- and six-body systems with unit charges. It is found that the ground bound $S(L = 0)-$states are stable in all six five-body $a b \mu e_2$ ions and in ten six-body $a b c \mu e_2$ quasi-molecules. As follows from accurate variational computations of the five-body $a b \mu e_2$ ions their internal structure is similar to the internal structure of the negatively charged hydrogen ion H$^{-}$. Analogously, we show that the internal structures of the six-body neutral $a b c \mu e_2$ quasi-molecules are similar to the structure of the two-center H$_{2}$ molecule which contains two heavy hydrogen nuclei and two bound electrons., Comment: arXiv admin note: text overlap with arXiv:1612.08730

9 pags., 6 figs., 1 tab., We present the results of classical molecular dynamics simulations of collision-induced fusion and fragmentation of C fullerenes, performed by means of the MBN Explorer software package. The simulations provide information on structural differences of the fused compound depending on kinematics of the collision process. The analysis of fragmentation dynamics at different initial conditions shows that the size distributions of produced molecular fragments are peaked for dimers, which is in agreement with a well-established mechanism of C fragmentation via preferential C emission.Atomic trajectories of the colliding particles are analyzed and different fragmentation patterns are observed and discussed. On the basis of the performed simulations, characteristic time of C emission is estimated as a function of collision energy.The results are compared with experimental time-of-flight distributions of molecular fragments and with earlier theoretical studies. Considering the widely explored case study of C–C collisions, we demonstrate broad capabilities of the MBN Explorer software, which can be utilized for studying collisions of a broad variety of nanoscale and biomolecular systems by means of classical molecular dynamics. Graphical abstract: [Figure not available: see fulltext.]., A.V. acknowledges the support by the European Commission through the FP7 Initial Training Network “ARGENT” (Grant Agreement No. 608163).

Hyperfine structures of the triplet $n^3S-$states in the four-electron Be-atom(s) and Be-like ions are considered. It is shown that to determine the hyperfine structure splitting in such atomic systems one needs to know the triplet electron density at the central atomic nucleus $\rho_T(0)$. We have developed the procedure which allows allows one to determine such an electron density $\rho_T(0)$ for arbitrary four-electron atoms and ions., Comment: PACS numbers: 31.30.Gs, 31.15.vj and 32.15.Fn

We report results of the calculation of the low-lying levels of neutral Si using a combination of the configuration interaction and many-body perturbation theory (CI+MBPT method). We treat Si I as an atom with four valence electrons and use two different starting approximations, namely $V^{N-2}$ and $V^{N-4}$. We conclude that both approximations provide comparable accuracy, on the level of 1%.

We consider the ionisation of atomic hydrogen by a strong infrared field. We extend and study in more depth an existing semi-analytical model. Starting from the time-dependent Schroedinger equation in momentum space and in the velocity gauge we substitute the kernel of the non-local Coulomb potential by a sum of N separable potentials, each of them supporting one hydrogen bound state. This leads to a set of N coupled one-dimensional linear Volterra integral equations to solve. We analyze the gauge problem for the model, the different ways of generating the separable potentials and establish a clear link with the strong field approximation which turns out to be a limiting case of the present model. We calculate electron energy spectra as well as the time evolution of electron wave packets in momentum space. We compare and discuss the results obtained with the model and with the strong field approximation and examine in this context, the role of excited states., 11 pages, 5 figures

In this manuscript we review the possibility of inducing large coherence in a macroscopic dense target by using adiabatic techniques. For this purpose we investigate the degradation of the laser pulse through propagation, which was also related to the size of the prepared medium. Our results show that, although adiabatic techniques offer the best alternative in terms of stability against experimental parameters, for very dense media it is necessary to engineer laser-matter interaction in order to minimize laser field degradation. This work has been triggered by the proposal of a new technique, namely Radiative Emission of Neutrino Pairs (RENP), capable of investigating neutrino physics through quantum optics concepts which require the preparation of a macrocoherent state., 10 pages, 10 figures

The electron correlation effects and Breit interaction as well as Quantum Electro-Dynamics (QED) effects were expected to have important contribution to the energy level and transition properties of heavy highly charged ions. The ground states [Ne]$3s^{2}3p^{6}3d^{2}$ and first excited states [Ne]3s$^{2}3p^{5}3d^{3}$ of W$^{54+}$ ion have been studied by using Multi-Configuration Dirac-Fock method with the implementation of Grasp2K package. A restricted active space was employed to investigate the correlation contribution from different models. The Breit interaction and QED effects were taken into account in the relativistic configuration interaction calculation with the converged wavefunction. It is found that the correlation contribution from 3s and 3p orbital have important contribution to the energy level, transition wavelength and probability of the ground and the first excited state of W$^{54+}$ ion.

We discuss the differences between two well-studied and related phenomena---coherent population trapping (CPT) and electromagnetically induced transparency (EIT). Many differences between the two---such as the effect of power in the beams, detuning of the beams from resonance, and the use of vapor cells filled with buffer gas---are demonstrated experimentally. The experiments are done using magnetic sublevels of the $ 1 \rightarrow 1 $ transition in the D$_2$ line of $^{87}$Rb., Comment: 9 pages, 13 figures

The interaction of a short, few-cycle light pulse and an atom which is prepared initially in a superposition of two stationary states is shown to exhibit strong signatures of atomic coherence. For a given waveform of the laser pulse, appropriate quantum mechanical relative phase between the constituents of the initial superposition can increase the ionization probability by a factor of three. A similarly strong effect can be observed when the waveform of the ionizing pulse is changed. These results allow for intuitive explanations, which are in agreement with the numerical integration of the time dependent Schr\"{o}dinger equation., Comment: 11 pages, 6 figures

The effects of quantum confinement on the momentum distribution of electrons confined within a cylindrical potential well have been analyzed. The motivation is to understand specific features of the momentum distribution of electrons when the electron behavior is completely controlled by the parameters of a non-isotropic potential cavity. It is shown that studying the solutions of the wave equation for an electron confined in a cylindrical potential well offers the possibility to analyze the confinement behavior of an electron executing one- or two-dimensional motion in the three-dimensional space within the framework of the same mathematical model. Some low-lying electronic states with different symmetries have been considered and the corresponding wave functions have been calculated; the behavior of their nodes and their peak positions with respect to the parameters of the cylindrical well has been analyzed. Additionally, the momentum distributions of electrons in these states have been calculated. The limiting cases of the ratio of the cylinder length H and its radius R 0 have been considered; when the cylinder length H significantly exceeds its radius R 0 and when the cylinder radius is much greater than its length. The cylindrical quantum confinement effects on the momentum distribution of electrons in these potential wells have been analyzed. The possible application of the results obtained here for the description of the general features in the behavior of electrons in nanowires with metallic type of conductivity (or nanotubes) and ultrathin epitaxial films (or graphene sheets) are discussed. Possible experiments are suggested where the quantum confinement can be manifested.

We present the results of a study on an optical-resonant cell filled by a vapor of the Rb atoms and coated with a non-stick polydimethylsiloxane (PDMS) polymer. We show that it is possible to define correctly the diffusion coefficient of the atoms in the coating using the geometric parameters of the cell and the vapor density in the cell volume only. The dependence of the diffusion coefficient on the cell curing time is presented. It is shown that the mysterious cell curing process can be explained in terms of the polymerization of the polymer coating by alkali atoms. The anomalous long dwell time of the Rb atoms on the PDMS coating is discussed as well.

The stereochemical properties of the ultracold ground state OH molecule in the presence of electric and magnetic fields are currently of considerable interest. For example, relevant quantities such as molecular alignment and orientation, calculated numerically by using large basis sets, have lately appeared in the literature. In this work, based on our recent exact solution to an effective eight-dimensional matrix Hamiltonian for the molecular ground state, we present analytic expressions for the stereochemical properties of OH. Our results require the solution of algebraic equations only, agree well with the aforementioned fully numerical calculations, provide compact expressions for simple field geometries, allow ready access to relatively unexplored parameter space, and yield straightforwardly higher moments of the molecular axis distribution., 8 pages, 9 figures

We consider a simple atomic two-body bound state system that is overall charge neutral and placed in a static electric and magnetic field, and calculate the magneto-electric response function as a function of frequency. This is done from first principles using a two-particle Hamiltonian for both an harmonic oscillator and Coulomb binding potential. In the high frequency limit, the response function falls off as 1/\omega^2 whilst at low frequencies it tends to a constant value., Comment: 6 pages, 4 figures

Transition wavelengths and probabilities for several 2p4 3p - 2p4 3s and 2p4 3d - 2p4 3p lines in fuorine-like neon ion (NeII) have been calculated within the multiconfiguration Dirac-Fock (MCDF) method with quantum electrodynamics (QED) corrections. The results are compared with all existing experimental and theoretical data.

We propose to couple a trapped single electron to superconducting structures located at a variable distance from the electron. The electron is captured in a cryogenic Penning trap using electric fields and a static magnetic field in the Tesla range. Measurements on the electron will allow investigating the properties of the superconductor such as vortex structure, damping and decoherence. We propose to couple a superconducting microwave resonator to the electron in order to realize a circuit QED-like experiment, as well as to couple superconducting Josephson junctions or superconducting quantum interferometers (SQUIDs) to the electron. The electron may also be coupled to a vortex which is situated in a double well potential, realized by nearby pinning centers in the superconductor, acting as a quantum mechanical two level system that can be controlled by a transport current tilting the double well potential. When the vortex is trapped in the interferometer arms of a SQUID, this would allow its detection both by the SQUID and by the electron., Comment: 13 pages, 5 figures

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., Comment: 10 pages, 4 tables

We discuss the role of the so-called Darwin-Foldy term in the evaluation of the proton and deuteron charge radii from atomic hydrogen spectroscopy and nuclear scattering data. The question of whether this term should be included or excluded from the nuclear radius has been controversially discussed in the literature. We attempt to clarify which literature values correspond to which conventions. A detailed discussion of the conventions appears useful because a recent experiment [R. Pohl et al., Nature vol. 466, p. 213 (2010)] has indicated that there is a discrepancy between the proton charge radii inferred from ordinary ("electronic") atomic hydrogen and muonic hydrogen. We also investigate the role of quantum electrodynamic radiative corrections in the determination of nuclear radii from scattering data, and propose a definition of the nuclear self energy which is compatible with the subtraction of the radiative corrections in scattering experiments., Comment: 8 pages, LaTeX, EPJD style

The hyperfine constants of the levels 2p 2 ( 3P)3s 4P J, 2p 2 ( 3P)3p 4P o J and 2p 2 ( 3P)3p 4D o J, deduced by Jennerich et al. [Eur. Phys. J. D 40, 81 (2006)] from the observed hyperfine structures of the transitions 2p 2 ( 3P)3s 4P J→ 2p 2 ( 3P)3p 4P o J and 2p 2 ( 3P)3s 4P J→ 2p 2 ( 3P)3p 4D o J recorded by saturation spectroscopy in the near-infrared, strongly disagree with the ab initio values of Jönsson et al. [J. Phys. B: At. Mol. Opt. Phys. 43, 115006 (2010)]. We propose a new interpretation of the recorded weak spectral lines. If the latter are indeed reinterpreted as crossover signals, a new set of experimental hyperfine constants is deduced, in very good agreement with the ab initio predictions. © 2010 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg., SCOPUS: ar.j, info:eu-repo/semantics/published

International audience; Metal atoms in solid and liquid helium-4 have attracted some interest either as a way to keep the atoms in a weakly perturbing matrix, or using them as a probe for the helium host medium. Laser sputtering with nanosecond pulsed lasers is the most often used method for atom production, resulting however in a substantial perturbation of the matrix. We show that a much weaker perturbation can be obtained by using femtosecond laser pulses with energy as low as 10 µJ. As an unexpected benefit, the atomic density produced is much higher.

We discuss the propagation of hydrogen atoms in static electric and magnetic fields in a longitudinal atomic beam spin echo (lABSE) apparatus. There the atoms acquire geometric (Berry) phases that exhibit a new manifestation of parity-(P-)violation in atomic physics. We provide analytical as well as numerical calculations of the behaviour of the metastable 2S states of hydrogen. The conditions for electromagnetic field configurations that allow for adiabatic evolution of the relevant atomic states are investigated. Our results provide the theoretical basis for the discussion of possible measurements of P-violating geometric phases in lABSE experiments., Comment: 27 pages, 10 figures

We investigate a possible mechanism for the autoionization of ultracold Rydberg gases, based on the resonant coupling of Rydberg pair states to the ionization continuum. Unlike an atomic collision where the wave functions begin to overlap, the mechanism considered here involves only the long-range dipole interaction and is in principle possible in a static system. It is related to the process of intermolecular Coulombic decay (ICD). In addition, we include the interaction-induced motion of the atoms and the effect of multi-particle systems in this work. We find that the probability for this ionization mechanism can be increased in many-particle systems featuring attractive or repulsive van der Waals interactions. However, the rates for ionization through resonant dipole coupling are very low. It is thus unlikely that this process contributes to the autoionization of Rydberg gases in the form presented here, but it may still act as a trigger for secondary ionization processes. As our picture involves only binary interactions, it remains to be investigated if collective effects of an ensemble of atoms can significantly influence the ionization probability. Nevertheless our calculations may serve as a starting point for the investigation of more complex systems, such as the coupling of many pair states proposed in [Tanner et al., PRL 100, 043002 (2008)].

The effect of finite nuclear mass on the magnetic-dipole transition probabilities between fine-structure levels of the same term is investigated. Based on a rigorous QED approach a nonrelativistic formula for the recoil correction to first order in m_e/M is derived. Numerical results for transitions of experimental interest are presented., 9 pages

International audience; We present a new evaluation of an 87Sr optical lattice clock using spin polarized atoms. The frequency of the 1S0-->3P0 clock transition is found to be 429 228 004 229 873.6 Hz with a fractional uncertainty of 2.6×10-15, a value that is comparable to the frequency difference between the various primary standards throughout the world. This measurement is in excellent agreement with a previous one of similar accuracy [Phys. Rev. Lett. 98, 083002 (2007)].

A system of metastable plus unstable states is discussed. The mass matrix governing the time development of the system is supposed to vary slowly with time. The adiabatic limit for this case is studied and it is shown that only the metastable states obtain the analogs of the dynamical and geometrical phase factors familiar from stable states. Abelian and non-abelian geometric phase factors for metastable states are defined., Comment: 30 pages

In this paper we review the different relativistic and QED contributions to energies, ionic radii, transition probabilities and Land\'e $g$-factors in super-heavy elements, with the help of the MultiConfiguration Dirac-Fock method (MCDF). The effects of taking into account the Breit interaction to all orders by including it in the self-consistent field process are demonstrated. State of the art radiative corrections are included in the calculation and discussed. We also study the non-relativistic limit of MCDF calculation and find that the non-relativistic offset can be unexpectedly large., Comment: V3, May 31st, 2007

We have studied the resonance fluorescence of a room-temperature rubidium vapor exited to the atomic 5P3/2 state (D2 line) by powerful single-frequency cw laser radiation (1.25 W/cm^2) in the presence of a magnetic field. In these studies, the slow, linear scanning of the laser frequency across the hyperfine transitions of the D2 line is combined with a fast linear scanning of the applied magnetic field, which allows us to record frequency-dependent Hanle resonances from all the groups of hyperfine transitions including V- and Lambda - type systems. Rate equations were used to simulate fluorescence signals for 85Rb due to circularly polarized exciting laser radiation with different mean frequency values and laser intensity values. The simulation show a dependance of the fluorescence on the magnetic field. The Doppler effect was taken into account by averaging the calculated signals over different velocity groups. Theoretical calculations give a width of the signal peak in good agreement with experiment.

We describe an experimental apparatus capable of achieving a high loading rate of strontium atoms in a magneto-optical trap operating in a high vacuum environment. A key innovation of this setup is a two dimensional magneto-optical trap deflector located after a Zeeman slower. We find a loading rate of 6x10^9/s whereas the lifetime of the magnetically trapped atoms in the 3P2 state is 54s., 12 pages, 16 figures

Absorption of infrared and visible radiation from stellar emission spectra by the negatively charged hydrogen ions H$^{-}$ is considered. The explicit formula for the photodetachment cross-section of the negatively charged hydrogen ion(s) is derived. Photodetachemnt cross-sections of the ${}^{\infty}$H$^{-}$, ${}^{3}$H$^{-}$ (or T$^{-}$), ${}^{2}$H$^{-}$ (or D$^{-}$) and ${}^{1}$H$^{-}$ ions are determined to high accuracy and for a large number of photo-electron momenta/energies. We introduce criteria which can be used to evaluate the overall quality of highly accurate wave functions of the hydrogen ion(s). One of these criteria is based on highly accurate calculations of the lowest order QED corrections in the negatively charged hydrogen ions, including ${}^{1}$H$^{-}$ (protium), ${}^{2}$H$^{-}$ (deuterium), ${}^{3}$H$^{-}$ (tritium) and model ion with the infinitely heavy nucleus ${}^{\infty}$H$^{-}$. An effective approach has been developed to calculate three-body integrals with the Bessel functions of different orders. Some preliminary evaluations of the phototdetachment cross-sections of the negatively charged hydrogen ions are performed. Inverse bremsstrahlung in the field of the neutral hydrogen atom is briefly discussed., arXiv admin note: substantial text overlap with arXiv:1110.3432

The diffusion radius of the 1S muonic hydrogen atoms in gaseous H_2 targets with various deuterium admixtures has been determined for temperatures T=30 and 300 K. The Monte Carlo calculations have been performed using the partial differential crosssections for $p\mu$ and $d\mu$ atom scattering from the molecules H$_2$, HD and D$_2$. These cross sections include hyperfine transitions in the muonic atoms, the muon exchange between the nuclei $p$ and $d$, and rotational-vibrational transitions in the target molecules. The Monte Carlo results have been used for preparing the time-projection chamber for the high-precision measurement of the nuclear $\mu^{-}$ capture in the ground-state $p\mu$ atom, which is now underway at the Paul Scherrer Institute., Comment: 8 pages, 10 figures, 1 table

Total electronic correlation correction to the binding energies of the isoelectronic series of Beryllium, Neon, Magnesium and Argon, are calculated in the framework of relativistic multiconfiguration Dirac-Fock method. Convergence of the correlation energies is studied as the active set of orbitals is increased. The Breit interaction is treated fully self-consistently. The final results can be used in the accurately determination of atomic masses from highly charged ions data obtained in Penning-trap experiments., version soumise 3/08/2005

A consistent quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. For the four-body scattering wave function, corresponding to the initial state, as well as for the antiprotonic helium wave function, appearing in the final tate, adiabatic approximations was used. Calculations were carried out for a wide range of antiprotonic helium states and incident energies of the antiproton. Obtained energy dependances of some cross sections show a rich low energy structure., Comment: 16 pages, 8 color pictures; the text, the bibliography, and the pictures were slightly corrected

International audience; In atom interferometry based on light-induced diffraction, the optical aberrations of the laser beam splitters are a dominant source of noise and systematic effect. In an atomic gyroscope, this effect is dramatically reduced by the use of two atomic sources. But it remains critical while coupled to fluctuations of atomic trajectories, and appears as a main source of noise to the long term stability. Therefore we measure these contributions in our setup, using cold Cesium atoms and stimulated Raman transitions.

Time domain deBroglie wave interferometry [Cahn et al, Phys. Rev. Lett. 79, 784] is applied to Rb87 atoms in a magnetic guide. A standing wave light field is carefully aligned along the guiding direction of the magnetic trapping potential from a soft-ferromagnetic 4-foil structure. A sequence of two standing wave pulses is applied to the magnetically trapped atoms. The backscattered light at the atomic density grating revival time is collected and detected via a heterodyning technique. In addition to the observed recoil oscillations that fit the interferometer theory for atoms in free space, we observe a decay of the interferometer contrast on a millisecond time scale with unexpected millisecond-scale oscillations. We find that the oscillating decay is explained by a residual variation of the linear trapping potential along the standing wave direction., Comment: 22 pages, 7 figures

International audience; We study the Josephson oscillations of two coupled elongated condensates. Linearized calculations show that the oscillating mode uniform over the length of the condensates (uniform Josephson mode) is unstable : modes of non zero longitudinal momentum grow exponentially. In the limit of strong atom interactions, we give scaling laws for the instability time constant and unstable wave vectors. Beyond the linearized approach, numerical calculations show a damped recurrence behavior : the energy in the Josephson mode presents damped oscillations. Finally, we derive conditions on the confinement of the condensates to prevent instabilities.

We present a systematic understanding of the rotational structure of a long-range (vibrationally highly-excited) diatomic molecule. For example, we show that depending on a quantum defect, the least-bound vibrational state of a diatomic molecule with $-C_n/r^n$ ($n>2$) asymptotic interaction can have only 1, 2, and up to a maximum of $n-2$ rotational states. A classification scheme of diatomic molecules is proposed, in which each class has a distinctive rotational structure and corresponds to different atom-atom scattering properties above the dissociation limit., 8 pages

Photoassociation of ultracold atoms induced by chirped picosecond pulses is analyzed in a non-perturbative treatment by following the wavepackets dynamics on the ground and excited surfaces. The initial state is described by a Boltzmann distribution of continuum scattering states. The chosen example is photoassociation of cesium atoms at temperature T=54 $\mu K$ from the $a^3 \Sigma_u^+(6s,6s)$ continuum to bound levels in the external well of the $0_g^-(6s+6p_{3/2})$ potential. We study how the modification of the pulse characteristics (carrier frequency, duration, linear chirp rate and intensity) can enhance the number of photoassociated molecules and suggest ways of optimizing the production of stable molecules., Comment: 40 pages, 12 figures, submitted to Eur. Phys. J. D

The cloud of cold atoms obtained from a magneto-optical trap is known to exhibit two types of instabilities in the regime of high atomic densities: stochastic instabilities and deterministic instabilities. In the present paper, the experimentally observed deterministic dynamics is described extensively. Three different behaviors are distinguished. All are cyclic, but not necessarily periodic. Indeed, some instabilities exhibit a cyclic behavior with an erratic return time. A one-dimensional stochastic model taking into account the shadow effect is shown to be able to reproduce the experimental behavior, linking the instabilities to a several bifurcations. Erraticity of some of the regimes is shown to be induced by noise.