arXiv subjects
Publications and source records attributed to V. V. Flambaum.
We use relativistic Hartree-Fock and configuration interaction methods to calculate the dependence of transition frequencies for singly ionized cobalt on the fine structure constant. The results are to be used in the search for variation of the fine structure constant in quasar absorption spectra.
We have considered an effect of atomic electrons due to the electronic bridge process on the nuclear $^{229m}$Th -- $^{229g}$Th transition in ^{229}$Th$^{3+}$. Based on a recent experimental result we assumed the energy difference between the isomeric and the ground nuclear states to be equal to 7.6 eV. We have calculated the ratios of the electronic bridge process probability Gamma_EB to the probability of the nuclear radiative transition (Gamma_N) for the electronic 5f_5/2 --> 6d_3/2,6d_5/2,7s and the 7s --> 7p_1/2,7p_3/2 transitions and found Gamma_EB/Gamma_N ~ 0.01-0.1 for the former and Gamma_EB/Gamma_N ~ 20 for the latter.
Our calculations have shown that the 5f_5/2-7s_1/2 23131 cm^{-1} transition from the ground state in the ion Th^{3+} is very sensitive to the temporal variation of the fine structure constant alpha (q=-75300 cm^{-1}). The line is very narrow, the ion has been trapped and laser cooled and the positive shifter line 5f_5/2-5f_7/2 4325 cm^{-1} (q=+2900 cm^{-1}) may be used as a reference. A comparison may also be made with a positive shifter in another atom or ion. This makes Th^{3+} a good candidate to search for the alpha variation.
We derive an expression for the magnetic blackbody shift of hyperfine transitions such as the cesium primary reference transition which defines the second. The shift is found to be a complicated function of temperature, and has a T^2 dependence only in the high-temperature limit. We also calculate the shift of ground-state p_1/2 hyperfine transitions which have been proposed as new atomic clock transitions. In this case interaction with the p_3/2 fine-structure multiplet may be the dominant effect.
The exchange interaction and correlations may produce a power-law decay instead of the usual exponential decrease of the wave function under potential barrier. The exchange-assisted tunneling vanishes in the classical limit, however, the dependence on the Planck constant h is different from that for a conventional single-particle tunneling.
Exchange interaction strongly influences the long-range behavior of localized electron orbitals and quantum tunneling amplitudes.In the Hartree-Fock approximation the exchange produces a power-law decay instead of the usual exponential decrease at large distances. To show that this effect is real (i.e. not a result of the approximation) we consider a simple model where different effects may be accurately analyzed. Applications include huge enhancement of inner electron ionization by a static electric field or laser field considered in Ref. M. Ya. Amusia, arxiv:0904.4395
Parity and time invariance violating electric dipole moment of $^{205}$Tl is calculated using the relativistic Hartree-Fock and configuration interaction methods and the many-body perturbation theory. Contributions from the interaction of the electron electric dipole moments with internal electric field and scalar-pseudoscalar electron-nucleon (T,P)-odd interaction are considered. The results are $d(^{205}{\rm Tl})=-582(20) d_e$ or $d(^{205}{\rm Tl})=-7.0(2)\times 10^{-18}C^{SP} e {\rm cm}$. Interpretation of the measurements are discussed. The results of similar calculations for $^{133}$Cs are $d(^{133}{\rm Cs})=124(4) d_e$ or $d(^{133}{\rm Cs})=0.76(2)\times 10^{-18}C^{SP} e {\rm cm}$.
According to GSI experiment Phys.Lett.B 664, 162 (2008), the rate of the daughter ion production by the K-shell electron capture (with neutrino emission) in H-like ions 142Pm, 140Pr and 152I is modulated with a period of 6 to 7 seconds. In PRL 103, 062502, 2009 by Ivanov and Kienle (also by Lipkin}) there is a claim that neutrino oscillations may explain this result. In arXiv:0811.2302 by Lambiase et al a different explanation is suggested which is based on the rotation of electron and nuclear spins. The aim of this Comment is to show why these explanations are not satisfactory and to discuss other possibilities.
The hyperfine structure constants of the lowest $s$ and $p_{1/2}$ states of superheavy elements Z=119 and Z= 120$^+$ are calculated using {\em ab initio} approach. Core polarization and dominating correlation effects are included to all orders. Breit and quantum electrodynamic effects are also considered. Similar calculations for Cs, Fr, Ba$^+$ and Ra$^+$ are used to control the accuracy. The dependence of the hyperfine structure constants on nuclear radius is discussed.
In this paper we report calculations of the relativistic corrections to transition frequencies (q factors) of Yb II for the transitions from the odd-parity states to the metastable state $4f^{13}6s^2 ^2F_{7/2}^o$. These transitions are of particular interest experimentally since they possess some of the largest q factors calculated to date and the $^2F_{7/2}^o$ state can be prepared with high efficiency. This makes Yb II a very attractive candidate for the laboratory search for variation of the fine-structure constant alpha.
We calculate the effect of variation in the light-current quark mass, $m_q$, on standard big bang nucleosynthesis. A change in $m_q$ at during the era of nucleosynthesis affects nuclear reaction rates, and hence primordial abundances, via changes the binding energies of light nuclei. It is found that a relative variation of $δm_q/m_q = 0.016 \pm 0.005$ provides better agreement between observed primordial abundances and those predicted by theory. This is largely due to resolution of the existing discrepancies for 7Li. However this method ignores possible changes in the position of resonances in nuclear reactions. The predicted 7Li abundance has a strong dependence on the cross-section of the resonant reactions 3He(d,p)4He and t(d,n)4He. We show that changes in $m_q$ at the time of BBN could shift the position of these resonances away from the Gamow window and lead to an increased production of 7Li, exacerbating the lithium problem.
Electric dipole moments of diamagnetic atoms of experimental interest are calculated using the relativistic Hartree-Fock and random-phase approximation methods, the many-body perturbation theory and configuration interaction technique. We consider P,T-odd interactions which give rise to atomic electric dipole moment in the second order of the perturbation theory. These include nuclear Schiff moment, P,T-odd electron-nucleon interaction and electron electric dipole moment. Interpretation of a new experimental constraint of a permanent electric dipole moment of $^{199}$Hg [W. C. Griffith {\it et al.}, Phys. Rev. Lett. {\bf 102}, 101601 (2009)] is discussed.
To search for the temporal variation of the fundamental constants one needs to know dependence of atomic transition frequencies on these constants. We study the dependence of the hyperfine structure of atomic $s$-levels on nuclear radius and, via radius, on quark masses. An analytical formula has been derived and tested by the numerical relativistic Hartree-Fock calculations for Rb, Cd$^+$, Cs, Yb$^+$ and Hg$^+$. The results of this work allow the use of the results of past and future atomic clock experiments and quasar spectra measurements to put constrains on time variation of the quark masses.
Based on measurements with the Effelsberg 100-m telescope, a multi-line study of molecular species is presented toward the gravitational lens system PKS1830-211. Obtaining average radial velocities and performing Large Velocity Gradient radiative transfer calculations, the aims of this study are (1) to determine the density of the gas, (2) to constrain the temperature of the cosmic microwave background, and (3) to evaluate the proton-to-electron mass ratio at redshift 0.9. Analyzing data from six rotational HC3N transitions (this includes the J=7-6 line, which is likely detected for the first time in the interstellar medium) we obtain about 2000 cm-3 for the gas density of the south-western absorption component. Again toward the south-western source, excitation temperatures of molecular species with optically thin lines and higher rotational constants are, on average, consistent with the expected temperature of the cosmic microwave background, T_CMB = 5.14 K. However, individually, there is a surprisingly large scatter which far surpasses expected uncertainties. A comparison of CS J=1-0 and 4-3 optical depths toward the weaker north-western absorption component results in an excitation temperature of 11 K and a 1-sigma error of 3 K. For the south-eastern main component, a comparison of velocities determined from ten optically thin NH3 inversion lines with those from five optically thin rotational transitions of HC3N, observed at similar frequencies, constrains potential variations of the proton-to-electron mass ratio, with respect to its present value, to <1.4 x 10^-6 with 3-sigma confidence. Also including optically thin rotational lines from other molecular species, it is emphasized that systematic errors are smaller than 1 km/s, corresponding to an uncertainty of 10-6.
The 7.6 eV electromagnetic transition between the nearly degenerate ground state and first excited state in the Th-229 nucleus may be very sensitive to potential changes in the fine-structure constant, $α= e^2/\hbar c$. However, the sensitivity is not known, and nuclear calculations are currently unable to determine it. We propose measurements of the differences of atomic transition frequencies between thorium atoms (or ions) with the nucleus in the ground state and in the first excited (isomeric) state. This will enable extraction of the change in nuclear charge radius and electric quadrupole moment between the isomers, and hence the $α$-dependence of the isomeric transition frequency with reasonable accuracy.
Ultracold molecules offer brand new opportunities to probe the variation of fundamental constants with unprecedented sensitivity. This paper summarizes theoretical background and current constraints on the variation of fine structure constant and electron-to-proton mass ratio, as well as proposals and experimental efforts to measure the variations based on ultracold molecules. In particular, we describe two novel spectroscopic schemes on ultracold molecules which have greatly enhanced sensitivity to fundamental constants: resonant scattering near Feshbach resonances and spectroscopy on close-lying energy levels of ultracold molecules.
Exchange interaction strongly influences the long-range behaviour of localised electron orbitals and quantum tunneling amplitudes. It violates the oscillation theorem (creates extra nodes) and produces a power-law decay instead of the usual exponential decrease at large distances. For inner orbitals inside molecules decay is $r^{-2}$, for macroscopic systems $\cos{(k_f r)} r^{-ν}$, where $k_f$ is the Fermi momentum and $ν=3$ for 1D, $ν=$3.5 for 2D and $ν=$4 for 3D crystal. Correlation corrections do not change these conclusions. Slow decay increases the exchange interaction between localized spins and the under-barrier tunneling amplitude. The under-barrier transmission coefficients in solids (e.g. for point contacts) become temperature-dependent.
We present an accurate ab initio method of calculating transition energies and isotope shifts in the 3d-transition metals. It extends previous work that combines the configuration-interaction calculation with many-body perturbation theory by including the effective three-body interaction and modification of the energy denominator. We show that these effects are of importance in Ti II. The need to develop methods that can accurately calculate isotope shifts in 3d-transition metals comes from studies of quasar absorption spectra that seek to measure possible variation of the fine-structure constant alpha over the lifetime of the Universe. Isotope shift can also be used to measure isotope abundances in gas clouds in the early Universe, which are needed in order to test models of chemical evolution.