Savely G. Karshenboim
Determination of the fine structure constant alpha and search for its possible variation are considered. We focus on a role of the fine structure constant in modern physics and discuss precision tests of quantum electrodynamics. Different methods of a search for possible variations of fundamental constants are compared and those related to optical measurements are considered in detail.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
继续探索
Configuration interaction in many-electron atoms may cause anomalies in the fine structure which make the intervals small and very sensitive to variation of the fine structure constant. Repeated precision measurements of these intervals over long period of time can put strong constrain on possible time variation of the fine structure constant. We consider the $5p^4 \ ^3$P$_{2,1,0}$ fine structure multiplet in the ground state of neutral tellurium as an example. Here the effect of change of the fine structure constant is enhanced about one hundred times in the relative change of the small energ…
Sensitivity of the frequencies of twenty two atomic transitions to the variation of the fine structure constant $α$ is calculated. The findings are to be used in search for possible variation of $α$ across our Galaxy using high quality spectroscopic data for stars similar to our Sun.
We show that the relative effect of variation of the fine structure constant in microwave transitions between very close and narrow rotational-hyperfine levels may be enhanced 2-3 orders of magnitude in diatomic molecules like LaS, LaO, LuS, YbF, etc. The enhancement is a result of cancellation between the hyperfine and rotational intervals.
Fundamental physical constants play important role in modern physics. Studies of their variation can open an interface to new physics. An overview of different approaches to a search for such variations is presented as well as possible reasons for the variations. Special attention is paid to laboratory searches.
Evidence that the fine structure constant, alpha, was different in an early epoch has recently been found in quasar (QSO) absorption spectra. An accurate laboratory measurement of alpha variation could help to distinguish between space and time variation of alpha and possibly confirm the QSO results. We have performed calculations of the relativistic energy shifts that a variation of alpha would cause in a wide range of atomic spectra. A laboratory measurement of how these transition frequencies vary over time is vital in determining whether alpha is varying today.
We study the electron correlation effects in the calculations of isotope shifts in Na and Mg+ using the relativistic coupled-cluster method. The trends of the correlation effects are explicitly discussed and comparison of the present results with the previously reported results are given. We also present the fine structure constant variation coefficients for many states in the above systems. From these results, it is possible to find out suitable transition lines those can be used as anchor and probe lines in finding possible variation in the fine structure constant.
Relativistic energy shifts of the low energy levels of Fe have been calculated using the Dirac-Hartree-Fock and configuration interaction techniques. The results are to be used in the search for the space-time variation of the fine structure constant in quasar absorption spectra. The values of the shifts are the largest among those used in the analysis so far. This makes Fe a good candidate for the inclusion into the analysis.
Dependence of transition frequencies on the fine structure constant $α=e^2/\hbar c$ is calculated for several many-electron systems which are used or planned to be used in the laboratory search for the time variation of the fine structure constant. In systems with a large number of electrons in open shells (from 11 to 15) the relative effects of the variation may be strongly enhanced. For the transitions which were considered before the results are in good agreement with previous calculations.
We perform accurate calculations of the dependence of transition frequencies in two valence electron atoms and ions on a variation of the fine structure constant, alpha. The relativistic Hartree-Fock method is used with many-body perturbation theory and configuration interaction methods to calculate transition frequencies. The results are to be used in atomic-clock-type laboratory experiments designed to test whether alpha varies in time.
We study transitions between ground and low-energy excited states of heavy ions corresponding to s-d single-electron transitions or s^2-d^2 double-electron transitions. The large nuclear charge Z and significant change in angular momentum of electron orbitals make these transitions highly sensitive to a potential variation in the fine-structure constant, alpha. The transitions may be considered as candidates for laboratory searches for space-time variation of alpha.
We study ultranarrow $5s_{1/2}$ - $4f_{5/2}$ transitions in Nd$^{13+}$ and Sm$^{15+}$ and demonstrate that they lie in the optical region. The transitions are insensitive to external perturbations. At the same time they are sensitive to the variation of the fine structure constant $α$. The fractional accuracy of the frequency of the transitions can be smaller than $10^{-19}$, which may provide a basis for atomic clocks of superb accuracy. Sensitivity to the variation of $α$ approaches $10^{-20}$ per year.
At present a number of current or proposed experiments are directed towards a search for a `new physics' by detecting variations of fundamental physical constants or violations of certain basic symmetries. Various problems related to the phenomenology of such experiments are considered here.
A possibility for fundamental constants to vary in time is suggested by theories unifying gravity with other interactions. In this article we examine proposals to use optical transitions of Sr, Dy, YbII and YbIII for the search of the time variation of the fine structure constant $α$. Frequencies of atomic transitions are calculated using relativistic Hartree-Fock method and configuration interaction technique. The effect of variation of $α$ on the frequencies is studied by varying $α$ in computer codes. Accuracy of measurements needed to improve current best limit on the time variation of $α$…
We study the Ho$^{14+}$ ion as a candidate for extremely accurate and stable optical atomic clock which is sensitive to the time variation of the fine structure constant. We demonstrate that the proposed system has all desired features including relatively strong optical electric dipole and magnetic dipole transitions which can be used for cooling and detection. Zero quadrupole moments for the relevant states in the clock transition allows interrogating multiple ions to improve the clock stability.
Radio-frequency electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored over an eight-month period to search for a variation in the fine-structure constant, $α$. The data provide a rate of fractional temporal variation of $α$ of $(-2.4\pm2.3)\times10^{-15}$ yr$^{-1}$ or a value of $(-7.8 \pm 5.9) \times 10^{-6}$ for $k_α$, the variation coefficient for $α$ in a changing gravitational potential. All results indicate the absence of significant variation at the present level of sensitivity. We also present initial results on laser coo…
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.
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 study atomic systems that are in the frequency range of optical atomic clocks and have enhanced sensitivity to potential time-variation of the fine structure constant, alpha. The high sensitivity is due to coherent contributions from three factors: high nuclear charge Z, high ionization degree, and significant differences in the configuration composition of the states involved. Configuration crossing keeps the frequencies in the optical range despite the large ionization energies. We discuss a few promising examples that have the largest alpha-sensitivities seen in atomic systems.
A brief review of the search for variation of the fine structure constant in quasar absorption spectra is presented. Special consideration is given to the role of atomic calculations in the analysis of the observed data. A range of methods which allow to perform calculations for atoms or ions with different electron structure and which cover practically all periodic table of elements is discussed. Critical compilation of the results of the calculations as well as a review of the most recent results of the analysis are presented.
Theories unifying gravity and other interactions suggest the possibility of spatial and temporal variation of physical ``constants''. Accuracy achieved for the atomic optical frequency standards (optical clocks) approaches the level when possible time evolution of the fine structure constant $α$ can be studied by comparisons of rates between clocks based on different atomic transitions in different atoms. The sensitivity to variation of $α$ is due to relativistic corrections which are different in different atoms ($\sim Z^2α^2$). We have calculated the values of the relativistic energy shifts …
It has been proposed that the radio-frequency electric-dipole (E1) transition between two nearly degenerate opposite-parity states in atomic dysprosium should be highly sensitive to possible temporal variation of the fine structure constant ($α$) [V. A. Dzuba, V. V. Flambaum, and J. K. Webb, Phys. Rev. A {\bf 59}, 230 (1999)]. We analyze here an experimental realization of the proposed search in progress in our laboratory, which involves monitoring the E1 transition frequency over a period of time using direct frequency counting techniques. We estimate that a statistical sensitivity of $|\adot…
We consider several transitions between narrow lines that have an enhanced sensitivity to a possible variation of the fine structure constant, alpha. This enhancement may allow a search to be performed with an effective suppression of the systematic sources of uncertainty that are unavoidable in conventional high-resolution spectroscopic measurements. In the future this may provide the strongest laboratory constraints on alpha variation.
Recently it was pointed out that transition frequencies in certain diatomic molecules have an enhanced sensitivity to variations in the fine-structure constant $α$ and the proton-to-electron mass ratio $m_p/m_e$ due to a near cancellation between the fine-structure and vibrational interval in a ground electronic multiplet [V.~V.~Flambaum and M.~G.~Kozlov, Phys. Rev. Lett.~{\bf 99}, 150801 (2007)]. One such molecule possessing this favorable quality is silicon monobromide. Here we take a closer examination of SiBr as a candidate for detecting variations in $α$ and $m_p/m_e$. We analyze the rovi…
Highly charged ions of heavy actinides as sensitive probes for time variation of the fine structure constant
本研究通过理论分析铀到锿的重锕系高电荷离子，发现多种电离度约10的离子中存在对精细结构常数变化敏感的6p-5f光学跃迁，其中部分可作为光钟跃迁，为探测精细结构常数时间变化提供了新候选体系。
We study electronic transitions in highly-charged Cf ions that are within the frequency range of optical lasers and have very high sensitivity to potential variations in the fine-structure constant, alpha. The transitions are in the optical despite the large ionisation energies because they lie on the level-crossing of the 5f and 6p valence orbitals in the thallium isoelectronic sequence. Cf16+ is a particularly rich ion, having several narrow lines with properties that minimize certain systematic effects. Cf16+ has very large nuclear charge and large ionisation energy, resulting in the larges…
We review a number of highly charged ions which have optical transitions suitable for building extremely accurate atomic clocks. This includes ions from Hf$^{12+}$ to U$^{34+}$, which have the $4f^{12}$ configuration of valence electrons, the Ir$^{17+}$ ion, which has a hole in almost filled $4f$ subshell, the Ho$^{14+}$, Cf$^{15+}$, Es$^{17+}$ and Es$^{16+}$ ions. Clock transitions in most of these ions are sensitive to variation of the fine structure constant, $α$ ($α= e^2/\hbar c$). E.g., californium and einsteinium ions have largest known sensitivity to $α$-variation while holmium ion look…
Transition frequencies of Fe II ion are known to be very sensitive to variation of the fine structure constant α. The resonance absorption lines of Fe II from objects at cosmological distances are used in a search for the possible variation of αin cause of cosmic time. In this paper we calculated the dependence of the transition frequencies on α^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 th…
Sensitivity to temporal variation of the fundamental constants may be strongly enhanced in transitions between narrow close levels of different nature. This enhancement may be realized in a large number of molecules due to cancelation between the ground state fine structure omega_f and vibrational interval omega_v (omega=omega_f - n omega_v is close to zero, delta omega/omega= K (2 delta alpha/alpha +0.5 delta mu/mu), K >>1, mu=m_p/m_e). The intervals between the levels are conveniently located in microwave frequency range and the level widths are very small. Required accuracy of the shift mea…
Over a period of eight months, we have monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These transition frequencies are highly sensitive to temporal variation of the fine-structure constant ($α$) due to relativistic corrections of large and opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a radio-frequency (rf) electric-dipole transition between them.…
We use the relativistic Hartree-Fock method, many-body perturbation theory and configuration-interaction method to calculate the dependence of atomic transition frequencies on the fine structure constant, alpha. The results of these calculations will be used in the search for variation of the fine structure constant in quasar absorption spectra.
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 show why a dynamically varying fine structure constant does not impact on the Webb group's analysis as suggested by Bekenstein. We also provide a limit on the size of a possible correction to the Dirac Hamiltonian caused by a perturbation due to a dynamically varying alpha in hydrogen.
We propose to use diatomic molecular ions to search for strongly enhanced effects of variation of fundamental constants. The relative enhancement occurs in transitions between nearly degenerate levels of different nature. Since the trapping techniques for molecular ions have already been developed, the molecules HBr$^+$, HI$^+$, Br$^+_2$, I$^+_2$, IBr$^+$, ICl$^+$, and IF$^+$ are very promising candidates for such future studies.
The precise measurement of molecular vibrational transition frequencies is useful in the search for variation in the proton-to-electron mass ratio μ. Homonuclear diatomic molecules are particularly advantageous for precise measurement because of the small Stark shift. This paper discusses the Stark and Zeeman shifts in the 16O2+ vibrational transition frequencies.To search for the variation μ(<10-17/yr), the X2Π1/2(v,J)=(0,1/2)-(v',1/2)(v'>1)in transition frequencies are much more advantageous than the transition frequencies between the X2Π1/2 v=21 and a4Π1/2 v=0 states, whose sensitivity to t…
We consider different options for the search for possible variations of the fundamental constants. We give a brief overview of the results obtained with several methods. We discuss their advantages and disadvantages with respect to simultaneous variations of all constants in both time and space in the range 10^{8}-10^{10} yr. We also suggest a few possibilities for the laboratory search. Particularly, we propose some experiments with the hyperfine structure of hydrogen, deuterium and ytterbium-171 and of some atoms with a small magnetic moment. Other suggestions are for some measurements of th…
We review recent activity searching for variations in the fundamental constants of nature in quasar absorption spectra and in the laboratory. While research in this direction has been ongoing for many decades, the topic has recently been stimulated by astronomical evidence for spatial variation in the fine-structure constant, alpha. This result could be confirmed using different quasar data and atomic clock measurements, but there are significant challenges to obtain the required accuracy. We review existing measurements and discuss some of the most promising systems where any variations would…
The relative effects of variation of the fine structure constant alpha=e^2/hc and dimensionless strong interaction parameter m_q/Lambda_{QCD} are enhanced 5-6 orders of magnitude in very narrow ultraviolet transition between the ground and first excited state in 229Th nucleus (energy (3.5 +/- 1) eV). Corresponding experiment has potential of improving sensitivity to the variation of the fundamental constants by 7-10 orders of magnitude (up to 10^{-23} per year).
Sensitivity of atomic transition frequencies to variation of the fine structure constant $α=e^2/\hbar c$ increases proportional to $Z^2$ where $Z$ is the nuclear charge. Recently several lines of heavy ions Ge II, Sn II and Pb II have been detected in quasar absorption spectra. We have performed accurate many-body calculations of $α^2$-dependence of transition frequencies ($q$-coefficients) for these atoms and found an order of magnitude increase in sensitivity in comparison with atomic transitions which were previously used to search for temporal and spatial variation of $α$ in quasar absorpt…
Searching for space-time variations of the constants of Nature is a promising way to search for new physics beyond General Relativity and the standard model motivated by unification theories and models of dark matter and dark energy. We propose a new way to search for a variation of the fine-structure constant using measurements of late-type evolved giant stars from the S-star cluster orbiting the supermassive black hole in our Galactic Center. A measurement of the difference between distinct absorption lines (with different sensitivity to the fine structure constant) from a star leads to a di…
We perform calculations of the dependence of nuclear magnetic moments on quark masses and obtain limits on the variation of the ratio of quark mass and strong interaction scale (m_q/Lambda_{QCD}) from recent atomic clock experiments with hyperfine transitions in H, Rb, Cs, Yb+, Hg+ and optical transition in Hg+. Experiments with Cd+, deuterium/hydrogen, molecule SF_6, Zeeman transitions in He_3/Xe are also discussed.
At present several groups are analyzing astrophysical data in a search for time-variation of the fine structure constant $α$. Here we discuss how to exclude systematic effects caused by the changes in the isotope abundances during the evolution of the universe. We suggest using particular combinations of the transition frequencies of O II, Al II, Al III, Si II and Mn II as anchors, which are insensitive to $α$-variation and to changes in isotope abundances. These anchors can be used to determine the cosmological redshift. Then, one can use other combinations of frequencies as probes for the ti…
We calculate sensitivity coefficients to $α$-variation for the fine-structure transitions (1,0) and (2,1) within $^3P_J[2s^2 2p^2]$ multiplet of the Carbon-like ions C I, N II, O III, Na VI, Mg VII, and Si IX. These transitions lie in the far infrared region and are in principle observable in astrophysics for high redshifts z~10. This makes them very promising candidates for the search for possible $α$-variation on a cosmological timescale. In such studies one of the most dangerous sources of systematic errors is associated with isotope shifts. We calculate isotope shifts with the help of rela…
Theories unifying gravity and other interactions suggest the possibility of spatial and temporal variation of physical ``constants'' in the Universe. Detection of high redshift absorption systems intersecting the sight lines towards distant quasars provide a powerful tool for measuring these variations. In the present paper we demonstrate that high sensitivity to variation of the fine structure constant alpha can be obtained by comparing cosmic and laboratory spectra of the Ni II ion. Relativistic effects in Ni II reveal many interesting features. The Ni II spectrum exhibits avoided level cros…
Aims. To obtain limits on the variation of the fine-structure constant alpha and the electron-to-proton mass ratio mu over different cosmological epochs. Methods. A new approach based on the comparison of redshifts of far infrared (FIR) fine-structure lines and low-lying rotational transitions in CO is proposed which is in principle more sensitive by a factor of 10 compared to QSO metal absorption lines. Results. Estimations of the quotient F = alpha^2/mu obtained for two distant quasars J1148+5251 (z = 6.42) and BR1202-0725 (z = 4.69) provide Delta F/F = (0.1+/-1.0)10^{-4} and (1.4+/-1.5)10^{…
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 frequencies 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.
In a recent paper [Phys. Rev. Lett. \textbf{93}, 130401 (2004)], we proposed the idea of expanding the space of variations in variational calculations of the energy by considering the approximate wave function $ψ$ to be a functional of functions $ χ: ψ= ψ[χ]$ rather than a function. The space of variations is expanded because a search over the functions $χ$ can in principle lead to the true wave function. As the space of such variations is large, we proposed the constrained-search-- variational method whereby a constrained search is first performed over all functions $χ$ such that the wave fun…
A new method for examining the possible space-time variation of the fine structure constant ($α$) is proposed. The technique uses a relatively simple measurement with an optical resonator to compare atom-stabilized optical frequency references. This method does not require that the exact frequency of each reference be measured, and has the potential to yield more than a 1000-fold improvement in experimental sensitivity to changes in $α$. A specific realization of an experiment using this method is discussed which can approach the precision of ${\dotα/α}\sim10^{-18}/τ$, where $τ$ is the measure…
We perform calculations of the dependence of nuclear magnetic moments on quark masses and obtain limits on the variation of $(m_q/Λ_{QCD})$ from recent measurements of hydrogen hyperfine (21 cm) and molecular rotational transitions in quasar absorption systems, atomic clock experiments with hyperfine transitions in H, Rb, Cs, Yb$^+$, Hg$^+$ and optical transition in Hg$^+$. Experiments with Cd$^+$, deuterium/hydrogen, molecular SF$_6$ and Zeeman transitions in $^3$He/Xe are also discussed.
High accuracy measurements in Mössbauer transitions open up the possibility to use them in the search for temporal and spatial variation of the fine-structure constant $α$, quark mass $m_q$, and dark matter field which may lead to the variation of $α$ and $m_q$. We calculate the sensitivity of nuclear transitions to variation of $α$ and $m_q$. Mössbauer transitions have high sensitivity to variation of quark mass $m_q$ and the strong interaction scale $Λ_{QCD}$, to which atomic optical clocks are not sensitive. The enhancement factors $K$, defined by $\frac{δf}{f} =K_{α}\frac{δα}α$ and $\frac{…
A high-precision relativistic calculations of Cd-like Nd$^{12+}$, Sm$^{14+}$ and Sn-like Pr$^{9+}$, Nd$^{10+}$ atomic properties is carried out using an approach that combines configuration interaction and a linearized coupled-cluster method. These ions have long-lived metastable states with transitions accessible by laser excitations, relatively simple electronic structure, high sensitivity to $α$ variation, and stable isotopes. Breit and QED corrections were included into the calculations. Energies, transition wavelengths, electric- and magnetic-multipole reduced matrix elements, lifetimes, …
We calculate bounds on the variation of the fine structure constant at the time of primordial nucleosynthesis and at the time of neutral hydrogen formation. We use these bounds and other bounds from the late universe to test Bekenstein model. We modify the Kawano code, CAMB and CosmoMC in order to include the possible variation of the fine structure constant. We use observational primordial abundances of $\De$, $\He$ and $\Li$, recent data from the Cosmic Microwave Background and the 2dFGRS power spectrum, to obtain bounds on the variation of $α$. We calculate a piecewise solution to the scala…
A method offering an order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant, alpha. Applying the technique to a sample of 30 absorption systems, spanning redshifts 0.5 < z< 1.6, obtained with the Keck I telescope, we derive limits on variations in alpha over a wide range of epochs. For the whole sample Delta(alpha)/alpha = -1.1 +/- 0.4 x 10^{-5}. This deviation is dominated by measurements at z > 1, where Delta(alpha)/alpha = -1.9 +/- 0.5 x 10^{-5}. For z < 1, Delta(alpha)/alpha = -0.2 +/- 0.4 x 1…
扫码添加微信好友，提出您的宝贵建议 👇
💡 备注请填写：网站反馈
发表机构由 AI 从论文文本抽取，如发现错误，欢迎反馈修正建议。