The generalized Bethe logarithm for tightly bound electrons

We derive a closed relativistic expression that makes it possible to calculate the self-energy of multiply charged ions in an external Coulomb field without resorting to a series expansion in powers of αZ. The expression contains the generalized Bethe logarithm for tightly bound electrons. We do numerical calculations of the self-energy for the 1s _1/2-electrons of multiply charged hydrogenlike ions. The proposed method allows for self-energy calculations for any values of the nuclear charge Z. Zh. éksp. Teor. Fiz. 112, 1197–1208 (October 1997)     

Study of J-T effect on the self-energy of electrons in manganite systems

We present here a theoretical study of the effect of Jahn-Teller(J-T) distortion on the self-energy of electrons in the CMR manganites. The model consists of the itinerant e _g electrons distorted by J-T effect and the localized t _2g core electrons carrying strong ferromagnetism due to Hund’s rule. The phonon interacts with the e _g electrons as well as the J-T distorted e _g band. The electron Green’s functions are calculated by Zubarev’s technique. The electron self-energy which carries all the information of the model is calculated from the Green’s function. The effect of J-T distortion, magnetism on the frequency and temperature dependent dynamic self-energy is presented in this paper. The results are discussed.     

Effect of constant-energy surface anisotropy on the thermoelectric figure-of-merit of the n-Bi2 (Te,Se,S)3 solid solutions

A study is reported of the thermoelectric and galvanomagnetic properties of n-Bi₂Te_3−x−y Se_xSe_y solid solutions for 0.12⩽x⩽0.36 and 0.12⩽y⩽0.21 within the 80–300 K temperature region. The thermoelectric figure-of-merit Z has been found to correlate with the parameters of the many-valley energy-band model including anisotropic carrier scattering. It is shown that a decrease in the constant-energy surface anisotropy and scattering anisotropy results in a growth of Z for optimum carrier concentrations in the solid solution. Fiz. Tverd. Tela (St. Petersburg) 41, 187–192 (February 1999)     

Screened self-energy correction to the 2<Emphasis Type="Italic">p</Emphasis><Subscript>3/2</Subscript>-2<Emphasis Type="Italic">s</Emphasis> transition energy in Li-like ions

We present an ab initio calculation of the screened self-energy correction for 1s² 2p_3/2 and 1s² 2s states of Li-like ions with nuclear charge numbers in the range Z = 12?100. The evaluation is carried out to all orders in the nuclear strength parameter Zα. This investigation concludes our calculations of all two-electron QED corrections for the 2p_3/2-2s transition energy in Li-like ions and thus considerably improves theoretical predictions for this transition for high-Z ions.     

The search for cosmic strangelets with the supersonic concorde and with JACEE's circumpolar balloon flight in Antarctica

The search for cosmic strangelet nuclei was carried out by two experiments with emulsion chambers. A balloon-borne JACEE emulsion chamber was flown at 3.5 g/cm² for 200 h in Antarctica (JACEE-10 experiment) and the Concorde flights were made by ECHOS at an atmospheric depth of 110 g/cm² between Paris and New York. No nuclei withZ⩾30 survived after traversing 60–120 g/cm² of the detector materials in the JACEE instruments. No evidence for a long mean free path were found in the zenith angle distribution forZ/β⩾26 nuclei. The exposure factor used by the JACEE was 72 m²hsr. The intensity upperbounds,I⩽(2.2–9.7)×10⁻²/m²h sr, were obtained for strangelets having an atmospheric attenuation length of 220−50 g/cm², which corresponds to the case for mass numberA=100–10000 andZ/β > 13. Concorde experiments (ECHOS) used both a thin and a thick emulsion chamber. The total exposure was 209 m² h sr and no candidates with chargeZ⩾30 were found. The largest track hadZ/β=28.6±1.29 withβ ∼ 1. Nuclei observed with charge 13⩽Z⩽30 were consistent with the survival intensity of ordinary nuclei. The flux bounds from the ECHOS experiments were I⩽(2.1–5.0) x 10⁻²/m²h for strangelets with mass number 100⩽A⩽1000.     

Neutral current cross-sections for neutrinos on protons

Defining the ratiosr _p =σ(vp →vx)/σ(vp →μ ⁻ x) and we obtain the bounds 0.28 ⩽r _p ⩽ 0.61 and using only the parton model and the data of CDHS group with iron target. We also give the complete set of parton-model relations which would allow the determination of all the neutral-current coupling constants from inclusive cross sections alone.     

Semi-analytic approach to higher-order corrections in simple muonic bound systems: Vacuum polarization,self-energy and radiative-recoil

The current discrepancy of theory and experiment observed recently in muonic hydrogen necessitates a reinvestigation of all corrections to contribute to the Lamb shift in muonic hydrogen (μH), muonic deuterium (μD), the muonic \hbox{³He{}^3{\rm He}} 3 He ion (denoted here as μ ³He⁺), as well as in the muonic \hbox{⁴He{}^4{\rm He}} 4 He ion (μ ⁴He⁺). Here, we choose a semi-analytic approach and evaluate a number of higher-order corrections to vacuum polarization (VP) semi-analytically, while remaining integrals over the spectral density of VP are performed numerically. We obtain semi-analytic results for the second-order correction, and for the relativistic correction to VP. The self-energy correction to VP is calculated, including the perturbations of the Bethe logarithms by vacuum polarization. Subleading logarithmic terms in the radiative-recoil correction to the 2S–2P Lamb shift of order α(Zα)⁵ μ ³ln(Zα) / (m _μ m _N ) are also obtained. All calculations are nonperturbative in the mass ratio of orbiting particle and nucleus.     

Two-loop self-energy correction in a strong Coulomb nuclear field

The two-loop self-energy correction to the ground-state energy levels of hydrogen-like ions with nuclear charges Z≥10 is calculated without the Zα expansion, where α is the fine-structure constant. The data obtained are compared with the results of analytical calculations within the Zα expansion; significant disagreement with the analytical results of order α²(Zα)⁶ has been found. Extrapolation is used to obtain the most accurate value for the two-loop self-energy correction for the 1s state in hydrogen.     

Contribution of three-electron diagrams of two-photon exchange to the energy of 2 s , 2 p 1/2, and 2 p 3/2 states of Li-like multiply charged ions

The contribution of three-electron diagrams of two-photon exchange to the energy of 2s, 2p _1/2, and 2p _3/2 states of Li-like ions is calculated. The consistent quantum-electrodynamic calculation is performed for the nuclear charge Z varying over a wide range with the correction for the finite size of the nucleus taken into account. All the contributions to the energy of the 2p _1/2−2s transition in Li-like ions with Z≥18 calculated to date are collected. __________ Translated from Optika i Spektroskopiya, Vol. 92, No. 3, 2002, pp. 375–384. Original Russian Text Copyright ? 2002 by Sysak, Erokhin, Shabaev.     

QED and hyperfine splitting in the 2s1/2−2p3/2 X-ray transition in lithium-like Bi80+

The measurement of the Bi⁸⁰⁺ 2s_1/2−2p_3/2 transition energy is discussed. The measurement resolved the hyperfine splitting of the (1s²2s) F=4,5 ground configuration and allowed a determination of the Lamb shift contributions with a precision of about 9 × 10^-4 providing the most accurate test of QED in a high-Z ion to date. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ranges of low-energy heavy ions in beryllium, boron, carbon, and silicon

Based on a theory of the passage of low-energy, heavy ions through matter, simple analytical expressions are obtained for calculating the average projected ranges of the ions and the rms deviations of the projected ranges. The theoretical and experimental ranges of heavy ions with atomic numbers 29⩽Z ₁⩽83 in targets of Be, B, C, and Si are compared. The theory is found to be in good agreement with experiment. Zh. Tekh. Fiz. 68, 33–36 (September 1998)     

About the perturbation factor for static and distributed quadrupole interaction in PAC spectroscopy

The traditional analysis of electric quadrupole interaction in disordered materials can give hyperfine parameters that would mask the actual values. As the relative distribution width δ increases, the correlation of this parameter with the rest produces strong shifts in all of them. Motivated by the values δ ⩾ 0.4 fitted in BaTi_1-xHf_xO₃ for 0 ⩽ x ⩽ 0.2 and other perovskites we extend previous calculations for Gaussian distribution function to the interval 0.3 ⩽ δ ⩽ 1. We also include the study of correlation between quadrupole parameters for Lorentzian distribution function in the 0 ⩽ δ ⩽ 1 interval. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Z = 82 shell closure in neutron-deficient Pb isotopes

Recent mass measurements show a substantial weakening of the binding-energy difference δ_2p(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + 2, N) in the neutron-deficient Pb isotopes. As δ_2p is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ_2p is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms of deformed ground states of Hg and Po isotopes. Received: 25 October 2001 / Accepted: 28 February 2002     

Rotation of the Fermi surface in the transition layer of bicrystals of an anisotropic metal

The Shubnikov-de Haas effect is investigated in bicrystals of p-type Bi_1−x Sb_x (0.063⩽x⩽0.088) alloys in static magnetic fields up to 15 T. The constant-energy surface of -holes in the transition layer of the bicrystals is found to be rotated ∼90° from its position in single domains (monoblocks). Fiz. Tverd. Tela (St. Petersburg) 39, 1713–1716 (October 1997)     

Fermilab top mass and modified Fritzsch mass matrices

Fritzsch like mass matrices with non-zero 22-elements both in U sector and D sector have been investigated in the context of latest data regardingm _t ^phys , |V _ub|, |V _cb|, |V _td| and |V _ts|. Unlike several other phenomenological models, the present model not only accommodates the value ofm _t ^phys in the range 150–240 GeV, encompassing the CDF and D0 values, but is also able to reproduce |V _cb| ≊0.040 and |V _ub/V_cb| = 0.08±0.02 and |V _td| is predicted to lie in the range 0.005–0.014. Further, the angles of the unitarity triangle, related to the CP-violating asymmetries, are calculated to be in the ranges −1.0⩽sin2α⩽−0.1, 0.6 ⩽sin2α⩽1.0 and 0.48⩽sin2β⩽0.56, which are in agreement with other recent calculations.     

Multiconfiguration Dirac-Fock results for forbidden transitions in the 2<Emphasis Type="Italic">p</Emphasis><Superscript>4</Superscript> configuration

Relativistic configuration interaction calculations with the inclusion of the Breit interaction, quantum electrodynamics and finite nuclear mass corrections have been carried out in the extended optimal level scheme using multiconfiguration Dirac-Fock wavefunctions on the forbidden transition probabilities for the 2p ⁴ ground state configuration of the oxygen isoelectronic sequence for 8 ⩽ Z ⩽ 42. Electric quadrupole and magnetic dipole transition probabilities are reported for transitions between several of these levels. Our results are compared with those from other theories and experiments. Our energy levels are in better agreement with experiment than other theories.     

Valence instability of uranium in U(Al1−x Gex)3

The electronic structure of U and Ge in the solid solutions U(Al_1−x Ge_x)₃ is investigated by measuring x-ray line shifts. It is shown that uranium has the mixed valence U³⁺ [Rn](5f ³)-U⁴⁺ [Rn](5f ²) over the entire composition range (0⩽x⩽1) and that the population of the uranium 5f shell increases by ∼0.28 5f electrons/U atom from UAl₃ (x=0) to UGe₃ (x=1). The electronic structure of Ge is close to the electronic structure of Ge metal over the entire composition range 0<x⩽1. No variation of the population of the Ge 4p shell is detected to within the experimental error (∼0.1 4p electrons/Ge atom) as the composition varies from x=0.2 to 1. It is established that the delocalization of a U 5f electron occurs as a result of its transition to the s or d band of the same uranium atom. Fiz. Tverd. Tela (St. Petersburg) 39, 1505–1508 (September 1997)     

带电体的自能系数及其规律的研究

文献上常给出个别特殊形状的带电体的自能公式,对一般带电体自能的特点及规律研究不够.本文先建立带电体自能系数的概念,然后计算几种常见对称带电体的自能和自能系数,由此找到带电体自能系数的定性与半定量的规律.     

X ray spectroscopic intercomparison between hydrogenic ions of different Z as a method for determining Lamb shifts

Novel methods for determining the 1s Lamb shift of hydrogenic ions are outlined. In one method the energy of a 2–1 transition in the hydrogenic ion of nuclear charge Z is compared to a 4–2 transition in the hydrogenic ion of charge 2Z. A second method exploits close coincidences between Lyman series transitions in ions of similar Z. This revised version was published online in August 2006 with corrections to the Cover Date.     

New double-magic nucleus <Superscript>96</Superscript>Zr and conditions for existence of new magic nuclei

New information about energies and occupation probabilities of neutron and proton single-particle (hole) subshells in even—even nuclei was obtained in previous studies applying the method of putting into correspondence all available data on one-nucleon pickup and stripping reactions. The most important and interesting resultwas identification of several nuclei as new magic ones. Namely, itwas found that a filling of the neutron 2d _5/2 subshell in ⁹⁶Zr makes this nuclide a magic one. Moreover, changes in proton subshell energies with increasing neutron number N are accompanied by an increasing energy gap between closed 2p _1/2 and empty 1g _9/2 subshells. Thus, the neutron number N = 56 appears to be a magic one if the proton number Z is equal to 40. The proton number Z = 40 manifests properties of the magic number in ⁹⁶Zr. Therefore, ⁹⁶Zr was identified as a new double-magic nucleus. Further investigations revealed that the energy of the first 2⁺ state E(2 ₁ ⁺ ) in ⁹⁶Zr is much higher than that in the neighboring isotopes and isotones, whereas the ratio E(4 ₁ ⁺ )/E(2 ₁ ⁺ ) and the quadrupole deformation parameter β2 are, vice versa, clearly lower. Moreover, the A dependence of the neutron separation energy B(n) in Zr isotopes has an irregularity at N = 56 which is typical of magic nuclei. As a result of these investigations, it was found that, near the Fermi energy, there are two closed subshells with the same (and large) angular momentum j = 5/2 (viz. π1f _5/2 and ν2d _5/2). We call this situation the jj connection. The magic numbers under discussion (Z = 40 and N = 56) are achieved at the points where both subshells are closed, and in addition, the closed subshell with j = 1/2, π2p _1/2, occurs above the proton π1f _5/2 subshell. This looks like a result of some additional attractive proton-neutron interaction. It was found that application of this scheme (jj connection) to other subshells reveals several other new magic nuclei: ⁵⁴Ca (closed π1d _3/2 and ν2p _3/2 together with closed ν2p _1/2), ³⁰S and ³⁰Si (closed π1d _5/2 and ν1d _5/2 together with closed (π/ν)2s _1/2), and ¹⁴O and ¹⁴C (closed π1p _3/2 and ν1p _3/2 together with closed ν2p _1/2). The text was submitted by the authors in English.