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We demonstrate the importance of electron correlation effects in the hyperfine structure constants of many low-lying states in 210Fr and 2l2Fr. This is achieved by calculating the magnetic dipole and electric quadrupole hyperfine structure constants using the Dirac-Fock approximation, second-order many-body perturbation theory, and the coupled-cluster method in the singles and doubles approximation in the relativistic framework. By combining our recommended theoretical results with the corresponding experimental values, improved nuclear magnetic dipole and electric quadrupole moments of the above isotopes are determined. In the present work, it is observed that there are large discrepancies between the hyperfine structure constants of the 7D5/2 state obtained from the experimental and theoretical studies, whereas good agreement is found for the other D5/2 states. Our estimated hyperfine constants for the 8P, 6D, 10S, and 11S states could be very useful as benchmarks for the measurement of these quantities. [ABSTRACT FROM AUTHOR]

Accurate knowledge of interaction potentials among the alkali-metal atoms and alkaline-earth ions is very useful in the studies of cold atom physics. Here we carry out theoretical studies of the long-range interactions among the Li, Na, K, and Rb alkali-metal atoms with the Ca+, Ba+, Sr+, and Ra+ alkaline-earth ions systematically, which are largely motivated by their importance in a number of applications. These interactions are expressed as a power series in the inverse of the internuclear separation R. Both the dispersion and induction components of these interactions are determined accurately from the algebraic coefficients corresponding to each power combination in the series. Ultimately, these coefficients are expressed in terms of the electric multipole polarizabilities of the above-mentioned systems, which are calculated using the matrix elements obtained from a relativistic coupled-cluster method and core contributions to these quantities from the random-phase approximation. We also compare our estimated polarizabilities with the other available theoretical and experimental results to verify accuracies in our calculations. In addition, we also evaluate the lifetimes of the first two low-lying states of the ions using the above matrix elements. Graphical representations of the dispersion coefficients versus R are given among all the alkaline ions with Rb. [ABSTRACT FROM AUTHOR]

Quadrupole shifts for three prominent clock transitions, [4f146S]²S1/2 → [4f145d]²D3/2, [4f146S]²S|S1/2 → [4f145d]²D5/2, and [4fl46s]²S1/2 [4f136S²]²F7/2, in the Yb+ ion are investigated by calculating values of the quadrupole moment (0) for the 5d3/2,5/2 and 4f7/2 states using the relativistic coupled-cluster (RCC) methods. We find an order of magnitude difference in the 0 value of the 4f7/2 state between our calculation and the experimental result, but our result concurs with that of other calculations carried out using many-body methods different from ours. However, our 0 value of the 53/2 state is in good agreement with the available experimental result and is highly precise. This enables us to estimate the quadrupole shift of the [4f146S]²S1/2 → [4f145d]²D3/2 clock transition more accurately. To justify the accuracies in our calculations, we evaluate the hyperfine structure constants of the 6s1/2, 5d3/2,5/2, and 4f7/2,5/2, states of the 171Yb+ ion using the same RCC methods and compare the results with the experimental values. We also determine the lifetime of the 5d3/2 state to address a discrepancy between conflicting values given by recent experiments. [ABSTRACT FROM AUTHOR]

We report the implementation of the equation-of-motion coupled-cluster (EOMCC) method in the fourcomponent relativistic framework with a spherical atomic potential to generate the excited states from a closedshell atomic configuration. This theoretical development will be very useful in carrying out high-precision calculations of various atomic properties in many atomic systems. We employ this method to calculate the excitation energies of many low-lying states in a few Ne-like highly charged ions, such as Cr XV, Fe XVII, Co XVIII, and Ni XIX ions, and compare them against their corresponding experimental values to demonstrate the accomplishment of the EOMCC implementation. The ions considered are appropriate to substantiate accurate inclusion of the relativistic effects in the evaluation of atomic properties and are also interesting for astrophysical studies. Investigation of the temporal variation of the fine-structure constant (a) obtained from astrophysical observations is a modern research problem for which we also estimate the a sensitivity coefficients in the above ions. [ABSTRACT FROM AUTHOR]

We have developed a one-electron detachment theory from a closed-shell atomic configuration in the relativistic Fock-space coupled-cluster ansatz. Using this method, we determine sensitivity coefficients to the variation of the fine-structure constant in the first three important low-lying transitions of the astrophysically interesting highly charged Mn IX, Fe X, Co XI, and Ni XII ions. The potential of this method has been assessed by evaluating the detachment energies of the removed electrons and determining the lifetimes of the atomic states in the above ions. To account for the sensitivity of the higher-order relativistic effects, we have used the four-component wave functions of the Dirac-Coulomb-Breit Hamiltonian with the leading-order quantum electrodynamics (QED) corrections. A systematic study has been carried out to highlight the importance of the Breit and QED interactions in the considered properties of the above ions. [ABSTRACT FROM AUTHOR]

We report here oscillator strengths, transition rates, branching ratios, and lifetimes due to the allowed transitions in the potassium (K) atom. We evaluate electric dipole (E1) amplitudes using an all-order relativistic many-body perturbation method. The obtained results are compared with previously available experimental and theoretical studies. Using the E1 matrix elements mentioned above and estimated from the lifetimes of the 4p ²P1/2,3/2 states, we determine precise values of static and dynamic polarizabilities for the first five low-lying states in the considered atom. The static polarizabilities of the ground and 4p ²P1/2,3/2 states in the present work are more precise than the available measurements in these states. Only the present work employs reladvistic theory to evaluate the polarizabilities in the 3d ²D3/2,5/2 states for which no experimental results are known with which to compare. We also reexamine "magic wavelengths" for the 4p ²P1/2 → 4s ²S1/2 and 4p² ²P3/2 → 4s ²S1/2 transitions due to the linearly polarized light, which are useful to perform the state-insensitive trapping of K atoms. [ABSTRACT FROM AUTHOR]

Nuclear quadrupole moments (Q's) in three isotopes of the potassium atom (K) with mass numbers 39,40, and 41 are evaluated more precisely in this work. The Q value of 39K is determined to be 0.0614(6) b by combining the available experimental result of the electric quadrupole hyperfine structure constant (B) with our calculated B/Q result of its 4P3/2 state. Furthermore, combining this Q value with the measured ratios Q(40K)/Q(39K) and Q(41K)/Q(39K), we obtain Q(40K)= -0.0764(8) b and Q(41K)= 0.0747(7) b, respectively. These results disagree with the sub-1% accuracy standard values recently quoted by Pyykkö [Mol. Phys. 106, 1965 (2008)]. The calculations were carried out by employing the relativistic coupled-cluster theory at the single, double, and involving important valence triple approximation. The accuracies of the calculated B/Q results can be viewed on the basis of comparison between our calculated magnetic dipole hyperfine structure constants (A's) with their corresponding measurements for many low-lying states. Both A and B results in a few more excited states are presented. Also, we find that the latest reported experimental hyperfine structure constant results for the 4P states in 39K are inconsistent with our calculations [ABSTRACT FROM AUTHOR]

Appraising the projected 10-18 fractional uncertainty in the optical frequency standards using singly ionized ions, we estimate the blackbody radiation (BBR) shifts due to the magnetic dipole (M1 ) and electric quadrupole (£2) multipoles of the applied external electromagnetic field. Multipolar scalar polarizabilities are determined for the singly ionized calcium (Ca+) and strontium (Sr+) ions using the relativistic coupled-cluster method, though the theory can be exercised for any single-ion clocks. The expected energy shifts for the respective clock transitions are estimated to be 4.38(3) x 10-4 Hz for Ca+ and 9.50(7) x 10-5 Hz for Sr+. These shifts are large enough and may be a prerequisite for the frequency standards to achieve the foreseen 10-18 precision goal. [ABSTRACT FROM AUTHOR]

We have carried out an extensive investigation of various spectroscopic properties of highly charged inert-gas ions using a relativistic coupled-cluster method through a one-electron detachment procedure. In particular, we have calculated the atomic states 2s²2p5²P3/2, 2s²2p5²P1/2, and 2s2p6²S1/2 in F-like inert-gas ions; 3s²3p5²P3/2, 3s²3p5²P1/2, and 3s3p6²S1/2 states in Cl-like Kr, Xe, and Rn; and 4s²4p5²P3/2, 4s²4p5²P1/2, and 4s4p6²S1/2 states in Br-like Xe and Rn. Starting from a single-reference Dirac-Hartree-Fock wave function, we construct our exact atomic states by including the dynamic correlation effects in an all-order perturbative fashion. Employing this method, we estimate the ionization potential energies of three low-lying orbitals present in their respective closed-shell configurations. Since the considered highly charged inert-gas ions exhibit huge relativistic effects, we have taken into account the corrections due to Breit interaction as well as from the dominant quantum electrodynamic correction such as vacuum polarization and self-energy effects in these systems. Using our calculated relativistic atomic wave functions and energies, we accurately determine various transition properties such as wavelengths, line strengths, oscillator strengths, transition probabilities, and lifetimes of the excited states. [ABSTRACT FROM AUTHOR]

Transitions among the first three low-lying states in the highly charged W13+, Ir16+, and Pt17+ ions are found to be strongly forbidden with wavelengths in the optical regime. By determining their energy levels, lifetimes, and other spectroscopic properties that are decisive quantities for estimating dominant systematics due to stray electromagnetic interactions in an experiment, we demonstrate that it can be possible to measure frequencies of the lowest forbidden transitions below a 10−19 precision level in the above ions, and hence, they seem to be suitable for frequency standards. We employ a sophisticated relativistic coupled cluster method to carry out calculations of these properties of the above states involving 4f- and 5s-core orbitals. We also found, by estimating their relativistic sensitivity coefficients, that these clock transitions can be highly sensitive to the tiny drift in the fine-structure constant αe. Consequently, a clock based on one of these ions, particularly Pt17+, could be used for corroborating the hypothesis of temporal and spatial variation in αe. [ABSTRACT FROM AUTHOR]