Experiments with antihydrogen (Hover ¯) for a study of matter-antimatter symmetry and antimatter gravity require ultracold Hover ¯ to reach ultimate precision. A promising path towards antiatoms much ...colder than a few kelvin involves the precooling of antiprotons by laser-cooled anions. Because of the weak binding of the valence electron in anions-dominated by polarization and correlation effects-only few candidate systems with suitable transitions exist. We report on a combination of experimental and theoretical studies to fully determine the relevant binding energies, transition rates, and branching ratios of the most promising candidate La^{-}. Using combined transverse and collinear laser spectroscopy, we determined the resonant frequency of the laser cooling transition to be ν=96.592 713(91) THz and its transition rate to be A=4.90(50)×10^{4} s^{-1}. Using a novel high-precision theoretical treatment of La^{-} we calculated yet unmeasured energy levels, transition rates, branching ratios, and lifetimes to complement experimental information on the laser cooling cycle of La^{-}. The new data establish the suitability of La^{-} for laser cooling and show that the cooling transition is significantly stronger than suggested by a previous theoretical study.
Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Laser spectroscopy in combination with ...modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear-model-independent way. Here we report on unique access to the differential mean-square charge radii of ^{252,253,254}No, and therefore to changes in nuclear size and shape. State-of-the-art nuclear density functional calculations describe well the changes in nuclear charge radii in the region of the heavy actinides, indicating an appreciable central depression in the deformed proton density distribution in ^{252,254}No isotopes. Finally, the hyperfine splitting of ^{253}No was evaluated, enabling a complementary measure of its (quadrupole) deformation, as well as an insight into the neutron single-particle wave function via the nuclear spin and magnetic moment.
Recent developments in frequency metrology and optical clocks have been based on electronic transitions in atoms and singly charged ions as references. The control over all relevant degrees of ...freedom in these atoms has enabled relative frequency uncertainties at a level of 10−18. This accomplishment not only allows for extremely accurate time and frequency measurements, but also to probe our understanding of fundamental physics, such as a possible variation of fundamental constants, a violation of the local Lorentz invariance, and the existence of forces beyond the standard model of physics. In addition, novel clocks are driving the development of sophisticated technical applications. Crucial for applications of clocks in fundamental physics are a high sensitivity to effects beyond the standard model and a small frequency uncertainty of the clock. Highly charged ions offer both. They possess optical transitions which can be extremely narrow and less sensitive to external perturbations compared to current atomic clock species. The large selection of highly charged ions offers narrow transitions that are among the most sensitive ones for the “new physics” effects. Recent experimental advances in trapping and sympathetic cooling of highly charged ions will in the future enable advanced quantum logic techniques for controlling motional and internal degrees of freedom and thus enable high-accuracy optical spectroscopy. Theoretical progress in calculating the properties of selected highly charged ions has allowed the evaluation of systematic shifts and the prediction of the sensitivity to the physics beyond the standard model. New theoretical challenges and opportunities emerge from relativistic, quantum electrodynamics, and nuclear-size contributions that become comparable with interelectronic correlations. This article reviews the current status of the field, addresses specific electronic configurations and systems which show the most promising properties for research, their potential limitations, and the techniques for their study.
SU(N) symmetry can emerge in a quantum system with N single-particle spin states when spin is decoupled from interparticle interactions. Taking advantage of the high measurement precision offered by ...an ultrastable laser, we report a spectroscopic observation of SU(N ≤ 10) symmetry in 87Sr. By encoding the electronic orbital degree of freedom in two clock states while keeping the system open to as many as 10 nuclear spin sublevels, we probed the non-equilibrium two-orbital SU(N) magnetism via Ramsey spectroscopy of atoms confined in an array of two-dimensional optical traps; we studied the spin-orbital quantum dynamics and determined the relevant interaction parameters. This study lays the groundwork for using alkaline-earth atoms as testbeds for important orbital models.
We propose 10 highly charged ions as candidates for the development of next generation atomic clocks, quantum information, and search for α variation. They have long-lived metastable states with ...transition wavelengths to the ground state between 170-3000 nm, relatively simple electronic structure, stable isotopes, and high sensitivity to α variation (e.g., Sm(14+), Pr(10+), Sm(13+), Nd(10+)). We predict their properties crucial for the experimental exploration and highlight particularly attractive systems for these applications.
We address the problem of the lattice Stark shifts in the Sr clock caused by the multipolar M1 and E2 atom-field interactions and by the term nonlinear in lattice intensity and determined by the ...hyperpolarizability. We develop an approach to calculate hyperpolarizabilities for atoms and ions based on a solution of the inhomogeneous equation which allows us to effectively and accurately carry out complete summations over intermediate states. We apply our method to the calculation of the hyperpolarizabilities for the clock states in Sr. We also carry out an accurate calculation of the multipolar polarizabilities for these states at the magic frequency. Understanding these Stark shifts in optical lattice clocks is crucial for further improvement of the clock accuracy.
We experimentally and theoretically determine the magic wavelength of the (5s2)S10−(5s5p)P03 clock transition of Cd111 to be 419.88(14) and 420.1(7) nm. To perform Lamb-Dicke spectroscopy of the ...clock transition, we use narrow-line laser cooling on the S10−P31 transition to cool the atoms to 6 μK and load them into an optical lattice. Cadmium is an attractive candidate for optical lattice clocks because it has a small sensitivity to blackbody radiation and its efficient narrow-line cooling mitigates higher order light shifts. We calculate the blackbody shift, including the dynamic correction, to be fractionally 2.83(8)×10−16 at 300 K, an order of magnitude smaller than that of Sr and Yb. We also report calculations of the Cd P11 lifetime and the ground state C6 coefficient.
This article reviews recent developments in tests of fundamental physics using atoms and molecules, including the subjects of parity violation, searches for permanent electric dipole moments, tests ...of the CPT theorem and Lorentz symmetry, searches for spatiotemporal variation of fundamental constants, tests of quantum electrodynamics, tests of general relativity and the equivalence principle, searches for dark matter, dark energy, and extra forces, and tests of the spin-statistics theorem. Key results are presented in the context of potential new physics and in the broader context of similar investigations in other fields. Ongoing and future experiments of the next decade are discussed.
This package of programs allows us to carry out relativistic calculations for many-electron atoms and ions. One can find energy levels and a number of atomic properties: g-factors, magnetic-dipole ...and electric-quadrupole hyperfine structure constants, electric- and magnetic-multipole transition amplitudes, and matrix elements of the parity nonconserving interactions. Method of calculation is based on a combination of conventional configuration interaction (CI) method and many-body perturbation theory (MBPT). The former explicitly accounts for the interaction between valence electrons, while the latter includes core–core and core–valence correlations. These two methods are combined to acquire benefits from both approaches and attain better accuracy.
Program title: CI-MBPT
Catalogue identifier: AEWV_v1_0
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEWV_v1_0.html
Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland
Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html
No. of lines in distributed program, including test data, etc.: 102640
No. of bytes in distributed program, including test data, etc.: 583539
Distribution format: tar.gz
Programming language:Fortran 90.
Computer: Intel Core i5 CPU, 3.2 GHz.
Operating system: Linux (CentOS 5, Ubuntu 12.04 LTS, SUSE 13.2).
RAM: 8 Gb
Classification: 2.1.
Nature of problem: Prediction of atomic or ionic energy levels and different observables in the framework of relativistic approach.
Solution method: The package of programs determines energy levels and associated many-electron wave functions for states of atoms and ions in the pure CI or CI+MBPT approximations. Using the wave functions, different atomic properties can be obtained, including g-factors, magnetic-dipole and electric-quadrupole hyperfine structure constants, electric- and magnetic-multipole transition amplitudes, P-odd and P,T-odd amplitudes.
Restrictions: The package is not designed for calculations of high Rydberg and autoionizing states. It becomes inefficient for the number of valence electrons exceeding four or five. It has not been tested for superheavy elements. The maximal number of Hartree–Fock–Dirac (HFD) orbitals when HFD equations are solved is 32.
Unusual features: One-electron orbitals outside the nucleus are defined on radial grid points. Inside the nucleus they are described in a form of the Taylor expansion over r/R, where R is the nuclear radius.
Additional comments: All programs have been compiled, linked, and tested with both “ifort” and freely available “gfortran”.
Running time: Changes from tens of minutes for atoms with two valence electrons to tens of hours for more complex systems.
We develop a broadly applicable approach that drastically increases the ability to predict the properties of complex atoms accurately. We apply it to the case of Ir^{17+}, which is of particular ...interest for the development of novel atomic clocks with a high sensitivity to the variation of the fine-structure constant and to dark matter searches. In general, clock transitions are weak and very difficult to identify without accurate theoretical predictions. In the case of Ir^{17+}, even stronger electric-dipole (E1) transitions have eluded observation despite years of effort, raising the possibility that the theoretical predictions are grossly wrong. In this work, we provide accurate predictions of the transition wavelengths and E1 transition rates for Ir^{17+}. Our results explain the lack of observations of the E1 transitions and provide a pathway toward the detection of clock transitions. The computational advances we demonstrate in this work are widely applicable to most elements in the periodic table and will allow us to solve numerous problems in atomic physics, astrophysics, and plasma physics.
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