Microwave and submillimeter molecular transition frequencies between nearly degenerated rotational levels, tunneling transitions, and mixed tunneling‐rotational transitions show an extremely high ...sensitivity to the values of the fine‐structure constant, α, and the electron‐to‐proton mass ratio, μ. This review summarizes the theoretical background on quantum‐mechanical calculations of the sensitivity coefficients of such transitions to tiny changes in α and μ for a number of molecules which are usually observed in Galactic and extragalactic sources, and discusses the possibility of testing the space‐ and time‐invariance of fundamental constants through comparison between precise laboratory measurements of the molecular rest frequencies and their astronomical counterparts. In particular, diatomic radicals CH, OH, NH+, and a linear polyatomic radical C3H in Π electronic ground state, polyatomic molecules NH3, ND3, NH2D, NHD2, H2O2, H3O+, CH3OH, and CH3NH2 in their tunneling and tunneling‐rotational modes are considered. It is shown that sensitivity coefficients strongly depend on the quantum numbers of the corresponding transitions. This can be used for astrophysical tests of Einstein's Equivalence Principle all over the Universe at an unprecedented level of sensitivity of ∼10−9, which is a limit three to two orders of magnitude lower as compared to the current constraints on cosmological variations of α and μ: Δα/α <10−6, Δμ/μ <10−7.
Microwave and submillimeter molecular transition frequencies between nearly degenerated rotational levels, tunneling transitions, and mixed tunneling‐rotational transitions show an extremely high sensitivity to the values of the fine‐structure constant, α, and the electron‐to‐proton mass ratio, μ. This review summarizes the theoretical background on quantum‐mechanical calculations of the sensitivity coefficients of such transitions to tiny changes in α and μ for a number of molecules.
A number of atoms and ions with complex valence configurations are considered as candidates for atomic clocks with high sensitivity to the possible variation of the fine‐structure constant. Present ...level of the theory is not sufficient to predict frequencies of the clock transitions with accuracy, required for the experiment. Here an approach is tested, where the second‐order perturbation theory is used to iteratively saturate configuration space for valence electrons. On the examples of scandium, titanium, and iodine, it is demonstrated that this improves the efficiency of the CI+MBPT method for systems with strong configuration interaction and/or more than three valence electrons.
Atomic theory cannot reliably predict spectra of atoms and ions with complex valence configurations. Here the second‐order perturbation theory is used to saturate valence configuration space. The examples of scandium, titanium, and iodine demonstrate that this improves the efficiency of the CI+MBPT method for systems with strong configuration interaction.
Blackbody radiation shifts in optical atomic clocks Safronova, M. S.; Kozlov, M. G.; Clark, C. W.
IEEE transactions on ultrasonics, ferroelectrics, and frequency control,
2012-March, 2012-Mar, 2012-03-00, 20120301, Letnik:
59, Številka:
3
Journal Article
Recenzirano
A review of recent theoretical calculations of blackbody radiation (BBR) shifts in optical atomic clocks is presented. We summarize previous results for monovalent ions that were obtained by a ...relativistic all-order single-double method, where all single and double excitations of the Dirac-Fock wave function are included to all orders of perturbation theory. A recently developed method for accurate calculations of BBR shifts in divalent atoms is then presented. This approach combines the relativistic all-order method and the configuration interaction method, which provides for accurate treatment of correlation corrections in atoms with two valence electrons. Calculations of the BBR shifts in B + , Al + , and In + have enabled us to reduce the present fractional uncertainties in the frequencies of their clock transitions as measured at room temperature: to 4 × 10 -19 for Al + and 10 -18 for B + and In + . These uncertainties approach recent estimates of the limits of precision of currently proposed optical atomic clocks. We discuss directions of future theoretical developments for reducing clock uncertainties resulting from blackbody radiation shifts.
An experiment utilizing a TlF molecular beam is being developed by the CeNTREX collaboration to search for hadronic interactions that violate both time-reversal (T) and parity (P) invariance. Here, ...we propose to use the same beam to look for a T-invariance conserving but P-nonconserving (PNC) effect induced by the anapole moment of the Tl nucleus, via a vector coupling of the two nuclear spins in TlF. To measure the nuclear anapole moment, the dc electric and magnetic fields in CeNTREX are replaced by rf fields resonant with a nuclear spin-flip transition. We adapt the relativistic coupled-cluster method in combination with relativistic density functional theory for the calculation of the molecular PNC spin-spin vector coupling constant that links the experimental signal with the anapole moment. The value of the P-conserving spin-spin coupling constant calculated within the same approach is found to be in good agreement with available experimental data.
The Dirac–Hartree–Fock plus many-body perturbation theory (DHF + MBPT) method has been used to calculate hyperfine structure constants for Fr. Calculated hyperfine structure anomaly for hydrogen-like ...ion is in good agreement with analytical expressions. It has been shown that the ratio of the anomalies for s and p1/2 states is weakly dependent on the principal quantum number. Finally, we estimate Bohr–Weisskopf corrections for several Fr isotopes. Our results may be used to improve experimental accuracy for the nuclear g factors of short-lived isotopes.
The weak interaction does not conserve parity, which is apparent in many nuclear and atomic phenomena. However, thus far, parity nonconservation has not been observed in molecules. Here we consider ...nuclear-spin-dependent parity-nonconserving contributions to the molecular Hamiltonian. These contributions give rise to a parity-nonconserving indirect nuclear spin-spin coupling which can be distinguished from parity-conserving interactions in molecules of appropriate symmetry, including diatomic molecules. We estimate the magnitude of the coupling, taking into account relativistic corrections. Finally, we propose and simulate an experiment to detect the parity-nonconserving coupling using liquid- or gas-state zero-field nuclear magnetic resonance of electrically oriented molecules and show that ^{1}H^{19}F should give signals within the detection limits of current atomic vapor-cell magnetometers.
Precision calculation of energy levels for four-valent Si I Imanbaeva, Raykhan T.; Kozlov, Mikhail G.; Konovalova, Elena A.
The European physical journal. D, Atomic, molecular, and optical physics,
05/2017, Letnik:
71, Številka:
5
Journal Article
Recenzirano
Odprti dostop
We report the results of our calculation of low-lying levels of neutral Si using a combination of the configuration interaction and many-body perturbation theory (CI+MBPT method). We treat Si I as an ...atom with four valence electrons, and use two different starting approximations, namely
V
N
−2
and
V
N
−4
. We conclude that both approximations provide comparable accuracy, on the level of 1%.
Graphical abstract
Development of new semisynthetic glycopeptides with improved antibacterial efficacy and reduced pseudoallergic reactions.
Semisynthetic glycopeptides 3-6 were synthesized from vancomycin (1) or ...eremomycin (2) by the condensation with pyrrolidine or piperidine. The minimum inhibitory concentration (MIC) for the new derivatives was measured by the broth micro-dilution method on a panel of clinical isolates of Staphylococcus and Enterococcus. Acute toxicity (50% lethal dose, maximum tolerated doses), antibacterial efficacy on model of systemic bacterial infection with
and pseudoallergic inflammatory reaction (on concanavalin A) of eremomycin pyrrolidide (5) were evaluated in mice according to standard procedures.
The eremomycin pyrrolidide (5) was the most active compound and showed a high activity against Gram-positive bacteria: vancomycin-susceptible staphylococci and enterococci (minimum inhibitory concentrations MICs 0.13-0.25 mg/L), as well as vancomycin-intermediate resistant
(MICs 1 mg/L). Antimicrobial susceptibility tested on a panel of 676 isolates showed that 5 had similar activity for the genera Staphylococcus and Enterococcus with MIC
=0.5 mg/L, while vancomycin had MIC
=1-2 mg/L. The number of resistant strains of
(vancomycin-resistant enterococci) (MIC =64 mg/L) with this value was 7 (8%) for vancomycin (1) and 0 for the compound 5. In vivo comparative studies in a mouse model of systemic bacterial infection with
demonstrated that the efficacy of 5 was notably higher than that of the original antibiotics 1 and 2. In contrast to 1, compound 5 did not induce pseudoallergic inflammatory reaction (on concanavalin A).
The new semisynthetic derivative eremomycin pyrrolidide (5) has high activity against staphylococci and enterococci including vancomycin-resistant strains. Compound 5 has a higher efficacy in a model of staphylococcal sepsis than vancomycin (1) or eremomycin (2). In striking contrast to natural antibiotics, the novel derivative 5 does not induce a pseudoallergic inflammatory reaction to concanavalin A and therefore has no histamine release activity. These results indicate the advantages of a new semisynthetic glycopeptide antibiotic eremomycin pyrrolidide (5) which may be a prospective antimicrobial agent for further pre-clinical and clinical evaluations.
A
bstract
We apply the differential equation technique to the calculation of the one-loop massless diagram with five onshell legs. Using the reduction to
ϵ
-form, we manage to obtain a simple ...one-fold integral representation exact in space-time dimensionality. The expansion of the obtained result in
ϵ
and the analytical continuation to physical regions are discussed.
Black-body radiation shifts and theoretical contributions to atomic clock research Safronova, M.S.; Dansha Jiang; Bindiya Arora ...
IEEE transactions on ultrasonics, ferroelectrics and frequency control/IEEE transactions on ultrasonics, ferroelectrics, and frequency control,
2010-Jan., 2010-Jan, 2010-01-00, 20100101, Letnik:
57, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A review of theoretical calculations of black-body radiation (BBR) shifts in various systems of interest to atomic clock research is presented. Calculations for monovalent systems, such as Ca + , Sr ...+ , and Rb are carried out using a relativistic all-order single-double method, where all single and double excitations of the Dirac-Fock wave function are included to all orders of perturbation theory. A recently developed method for accurate calculations of BBR shifts in divalent atoms such as Sr is discussed. This approach combines the relativistic all-order method and the configuration interaction method. The evaluation of uncertainties in theoretical values of BBR shifts is discussed in detail.
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