Accurate relativistic many-body calculations of van der Waals coefficients C_8 and C_10 for alkali-metal dimers

We consider long-range interactions between two alkali-metal atoms in their respective ground states. We extend the previous relativistic many-body calculations of C_6 dispersion coefficients [Phys.Rev. Lett. {\bf 82}, 3589 (1999)] to higher-multipole coefficients C_8 and C_10. A special attention is paid to usually omitted contribution of core-excited states. We calculate this contribution within relativistic random-phase approximation and demonstrate that for heavy atoms core excitations contribute as much as 10% to the dispersion coefficients. We tabulate results for both homonuclear and heteronuclear dimers and estimate theoretical uncertainties. The estimated uncertainties for C_8 coefficients range from 0.5% for Li_2 to 4% for Cs_2.Comment: 12 pages, submitted to Journal of Chemical Physic

Transition Operators Entering Neutrinoles Double Electron Capture to Excited Nuclear States

We construct the effective transition operators relevant for neutrinoless double electron capture leading to final nuclear states different than $0^{+}$. From the structure of these operators we see that, if such a process is observed experimentally, it will be very helpful in singling out the very important light neutrino mass contribution from the other lepton violating mechanismsComment: 9 LaTex pages, 2 figures, 1 table, references adde

Relativistic corrections to isotope shift in light ions

We calculate isotope mass shift for several light ions using Dirac wave functions and mass shift operator with relativistic corrections of the order of $(\alpha Z)^2$. Calculated relativistic corrections to the specific mass shift vary from a fraction of a percent for Carbon, to 2% for Magnesium. Relativistic corrections to the normal mass shift are typically smaller. Interestingly, the final relativistic mass shifts for the levels of one multiplet appear to be even closer than for non-relativistic operator. That can be important for the astrophysical search for possible $\alpha$-variation, where isotope shift is a source of important systematic error. Our calculations show that for levels of the same multiplet this systematics is negligible and they can be used as probes for $\alpha$-variation.Comment: 7 pages, 5 tables, revtex

Transition frequency shifts with fine structure constant variation for Fe II: Breit and core-valence correlation correction

Transition frequencies of Fe II ion are known to be very sensitive to variation of the fine structure constant \alpha. The resonance absorption lines of Fe II from objects at cosmological distances are used in a search for the possible variation of \alpha in cause of cosmic time. In this paper we calculated the dependence of the transition frequencies on \alpha^2 (q-factors) for Fe II ion. We found corrections to these coefficients from valence-valence and core-valence correlations and from the Breit interaction. Both the core-valence correlation and Breit corrections to the q-factors appeared to be larger than had been anticipated previously. Nevertheless our calculation confirms that the Fe II absorption lines seen in quasar spectra have large q-factors of both signs and thus the ion Fe II alone can be used in the search for the \alpha-variation at different cosmological epochs.Comment: 7 pages, submitted to Phys. Rev.

Development of a configuration-interaction + all-order method for atomic calculations

We develop a theoretical method within the framework of relativistic many-body theory to accurately treat correlation corrections in atoms with few valence electrons. This method combines the all-order approach currently used in precision calculations of properties of monovalent atoms with the configuration-interaction approach that is applicable for many-electron systems. The method is applied to Mg, Ca, Sr, Zn, Cd, Ba, and Hg to evaluate ionization energies and low-lying energy levels.Comment: 10 page

Relativistic calculations of the K-K charge transfer and K-vacancy production probabilities in low-energy ion-atom collisions

The previously developed technique for evaluation of charge-transfer and electron-excitation processes in low-energy heavy-ion collisions [I.I. Tupitsyn et al., Phys. Rev. A 82, 042701(2010)] is extended to collisions of ions with neutral atoms. The method employs the active electron approximation, in which only the active electron participates in the charge transfer and excitation processes while the passive electrons provide the screening DFT potential. The time-dependent Dirac wave function of the active electron is represented as a linear combination of atomic-like Dirac-Fock-Sturm orbitals, localized at the ions (atoms). The screening DFT potential is calculated using the overlapping densities of each ions (atoms), derived from the atomic orbitals of the passive electrons. The atomic orbitals are generated by solving numerically the one-center Dirac-Fock and Dirac-Fock-Sturm equations by means of a finite-difference approach with the potential taken as the sum of the exact reference ion (atom) Dirac-Fock potential and of the Coulomb potential from the other ion within the monopole approximation. The method developed is used to calculate the K-K charge transfer and K-vacancy production probabilties for the Ne$(1s^2 2s^2 2p^6)$ -- F$^{8+}(1s)$ collisions at the F$^{8+}(1s)$ projectile energies 130 keV/u and 230 keV/u. The obtained results are compared with experimental data and other theoretical calculations. The K-K charge transfer and K-vacancy production probabilities are also calculated for the Xe -- Xe$^{53+}(1s)$ collision.Comment: 16 pages, 4 figure

High accuracy calculation of 6s -> 7s parity nonconserving amplitude in Cs

We calculated the parity nonconserving (PNC) 6s -> 7s amplitude in Cs. In the Dirac-Coulomb approximation our result is in a good agreement with other calculations. Breit corrections to the PNC amplitude and to the Stark-induced amplitude $\beta$ are found to be -0.4% and -1% respectively. The weak charge of $^{133}$Cs is $Q_W=-72.5 \pm 0.7$ in agreement with the standard model.Comment: 4 pages, LaTeX2e, uses revtex4.cls, submitted to PR

Augmentation of pedicle screws using bone grafting in patients with spinal osteoporosis

The aim of the study was to develop a new method of vertebral augmentation based on autologous and allogeneic bone chips to be used in pedicle screw fixation and to compare this method with the technique based on polymethyl methacrylate (PMMA). Materials and Methods. This prospective non-randomized study included 164 patients with degenerative pathologies or traumatic injuries of the lumbar spine and transitional thoracolumbar segments; 153 of the operated patients were followed up for 18 months. In these patients, radiodensity of the cancellous bone tissue was below 110 HU by the Hounsfield scale. Patients with degenerative spinal disorders underwent pedicle screw fixation using transforaminal interbody fusion; patients with traumatic spinal injuries underwent intermediate pedicle screw fixation, and those with a loss of vertebral body height by \u3e50% underwent anterior fusion. The patients were divided into three groups: in group 1 (n=39), bone tissue augmentation was performed using PMMA; in group 2 (n=21), augmentation was done with bone chips; in group 3 (n=93), no augmentation was performed (control group). The follow-up period was 12 months; cases with fixator breakage or loosening were recorded. Results. After augmentation with PMMA, 11 cases (28.2%) of fixator destabilization were detected. With bone chips, fixator instability developed in 2 patients (9.5%) only, whereas in patients operated without augmentation, the instability was observed in 43 cases (46.2%). With PMMA augmentation, the incidence rate of fixator destabilization did not significantly differ from that in the control group (p=0.0801), while the use of bone chips resulted in a statistically significant decrease of this index compared to the control group (p=0.0023). A logistic regression analysis confirmed the superiority of the developed method over the PMMA-based vertebral augmentation. Conclusion. The use of bone chips for vertebral augmentation provides a statistically significant decrease in the incidence of pedicle screw fixator destabilization in the post-operative period. By reducing the risk of proximal loosening and eliminating the risk of bone cement drainage into the spinal canal and vascular bed, the proposed method may become especially effective in patients with impaired bone density

Probing the nuclide 180W for neutrinoless double-electron capture exploration

The mass difference of the nuclides 180W and 180Hf has been measured with the Penning-trap mass spectrometer SHIPTRAP to investigate 180W as a possible candidate for the search for neutrinoless doubleelectron capture. The Q-value was measured to 143.20(27)keV. This value in combination with the calculations of the atomic electron wave functions and other parameters results in a half-life of the 0+ \rightarrow 0+ ground-state to ground-state double-electron capture transition of approximately 5\cdot10E27 years/^2