Enhanced isospin dependence of the empirical particle-hole effective interaction

The separation betweenT=0 andT=1 centroids of the empirical effective interaction is fairly large for the (d ₃ ^2/−1 f _7/2)JT particle-hole interaction as compared to nearby (f _7/2)² JT and (d _5/2)² JT particle-particle interactions. This interesting feature of the empirical effective interaction is shown to arise as a consequence of renormalization of the effective interaction as one truncates the configuration space from (s−d)⁻¹(f−p)¹ to (d ₃ ^2/−1 f _7/2) and from (f−p)² and (s−d)² configurations to (f _7/2)² and (d _5/2)² respectively.     

A ligand field theory analysis of the spectra of the t 2g 3 levels of IrF6

Calculations and experimental data are presented for the t _2g ³ molecular levels of IrF₆ which imply that a substantial interaction takes place between these 5d³-configuration states and charge transfer states at ca. 20 000 cm^-1. This t _2g ³-charge transfer state configuration interaction is so extensive that the five t _2g ³ levels can only be fit with physically unreasonable values of the Racah (electrostatic) parameters and a spin orbit coupling parameter that is not consistent with expectations for 5d-series transition metal hexafluorides. Parameter values presented for IrF₆ are thus determined from the lowest three levels only, as these should experience the smallest relative shift due to configuration interaction: B = 297 cm^-1, C = 1167 cm^-1, ζ_5d = 4182 cm^-1, and 10Dq = 35 000 cm^-1. In order to corroborate the assertion that t _2g ³-charge transfer configuration interaction is an important factor for the determination of IrF₆ crystal and molecular properties, a number of t _2g ³ spectroscopic properties, which turn out to be quite sensitive to charge transfer state admixture, were studied theoretically and experimentally. These include gas-to-crystal shifts, site splittings, and Jahn-Teller interactions; comparison of calculated and experimental values clearly substantiate the conclusion that there is a strong influence of charge transfer states on the nature of the 5d³-t _2g ³ manifold. Finally, new data for the Γ_8g (² E_g ) and Γ_6g (² T _1g ) states at 1·2 μm are given, completing the data set for the t _2g ³ transitions of IrF₆.     

Model-independent analysis of the neutral-current interaction in the inclusive neutrino reactions

On the basis of some general assumptions on the deep inelastic structure functions, such as scaling and chiral symmetry we determine the values of {(H _V ³)²+(H _A ³)²}+η{(H _V ⁰)²+(H _A ⁰)²} andH _V ³ H _A ³+ηH _V ⁰ H _A ⁰ whereH _V ^3,0 andH _A ^3,0 are the four coupling constants characterizing the hadronic neutral current andη is the ratio of the isoscalar to isovector structure functions. General expressions are given for the kinematical averages 〈v〉 and 〈Q ²〉 for the neutral-current reactions in terms of the coupling constants. This analysis does not depend on the validity of the quark-parton model.     

Theory of Gravitational-Inertial Field of Universe. IV. The Universe and the Microcosm

On basis of principle of discreteness of the space and time the following relations are obtained Λ_oM_oc = 2π?, τ_oE_o = 2π? and c² = 2GM_o/Λ_o giving the values of fundamental elements of length Λ_o ≈ (?G/c³)^1/2, mass M_o ≈ (?c/G)^1/2, time τ_o ≈ (?G/c⁵)^1/2 and energy E_o ≈ (?c⁵/G)^1/2. The geon crown of any critical system and the crown of the Universe must have a thickness equal to the fundamental length Λ_o = 2(π?G/c³)^1/2 = 5.74. 10^?33 cm. Each critical system has its specific (most probable) quantum with an average invariant mass which in the case of the Universe is equal to (2π²?H_u/Gc)^1/3 ≈ 300 m_e where H_u is Hubble's constant. There are all reasons to consider the universal virtual quanta of an invariant mass m_u ≈ 300 m_e as carriers of gravitational, electromagnetic and nuclear fields in the Universe.     

NMR-analysis of the conduction electron polarization at the gadolinium site in ferromagnetic intermetallic compounds

We have studied the zero field spin echo NMR of ¹⁵⁵Gd, ¹⁵⁷Gd, ¹³⁹La, ¹⁹¹Ir and ¹⁹³Ir in the compounds Gd_xLa_1-x Ir₂ and Gd_xY_1-xIr₂. The ¹³⁹La resonance in particular proved useful as probe for the contribution (H_N) of the hyperfine field at the Gd site in GdIr₂ which is due to the polarizing influence of all the other Gd moments in the lattice. In GdIr₂ the contribution H_N was found to be positive; it is due for about 56% to the four nearest neighbour atoms. The part of H_N coming from the second and third nearest neighbour atoms has the same sign (positive) as that of the nearest neighbours. We show how the varying magnitude and sign of H_N in intermetallic compounds of Gd can be used to estimate the relative importance of 5d electrons in the indirect coupling of the localized rare-earth moments.     

New investigation of the decay of the high-spin isomer in 151Er

The decay of the T _1/2 = 420 ns isomer in ¹⁵¹Er has been reinvestigated. The multipolarities of the decaying transitions have been established by measuring the electron conversion coefficients. An I ^π = 67/2⁻ assignment is proposed for this isomer with a π[h ₁₁^2/4 d ₃^2/1 d ₅^2/−1]⊗ν[f _7/2 h _9/2 h ₁₁^2/−1] configuration.     

Majorana mass of the electron-muon Dirac neutrino and the fermion masses

The left-handed electron and muon neutrinos are considered to be Majorana neutrinos with equal mass. They have oppositeCP parities and are equivalent to a single Dirac neutrino. These neutrinos are shown to have a Majorana mass of about 6.5 eV. The relatively large mass of their charged leptons is due to their γ₅ coupling with the Higgs scalars By expressing the Higgs scalars as Clebsch-Gordon type of combinations ofZ andD neutral vector bosons with appropriate quantum numbers, it is shown that 2m _e m _μ /(m _e ² +m _μ ² )=(g_{v/g A}) _eμ ² , whereg _v andg _A are the vector and axial vector coupling constants, respectively, ofZ (orD) with the leptonse and μ. Weinberg mixing parametersx _L =e²/g _L ² andx _R =e ²/g _R ² are determined to be 0.2254 and 0.2746, respectively. In the quark sector the Cabibbo angle is about 13°11′ and the masses oft andb quarks are found to be respectively 134.2 and 4.69 GeV.     

Spectroscopic and ab initio characterization of the conformational states of the bis(perfluoro‐ ethanesulfonyl)imide anion (BETI−)

Ab initio calculations were combined with infrared and Raman studies to spectroscopically distinguish the two conformers of the BETI⁻ or bis(perfluoroethanesulfonyl)imide anion, [N(SO₂C₂F₅)₂]⁻, as was previously done for [N(SO₂CF₃)₂]⁻, the TFSI⁻ anion. BETI⁻ is predicted to exist, as does TFSI⁻, in two conformational states of C₂ and C₁ symmetries, the former being more stable by about 6 kJ mol⁻¹. This conformational isomerism produces weak Raman splittings that can be resolved only at low temperatures. Thus, solutions of LiBETI with glymes cooled down to 113 K exhibit a very intense Raman doublet at ∼745–740 cm⁻¹ characteristic of a quenched conformational equilibrium between the C₂ and C₁ conformers. Annealing of the (G3)₂:LiBETI solvate, where G3 is triglyme, leads to an ordered crystalline phase with all the anions in the C₂ conformation, as in the reference salt Me₄NBETI. This conclusion cannot be extended to all the systems in which the BETI⁻ anion interacts weakly with the cation, however, since the diglyme solvate, (G2)₂:LiBETI, contains both C₁ and C₂ anion conformers (in 2:1 ratio) at low temperatures independent of the sample's thermal history. The conformational splittings are larger in infrared, as illustrated by two absorption bands at 601 and 615 cm⁻¹ associated with the C₂ and C₁ anion conformers, respectively. It is possible to follow the relative intensities of these bands in a LiBETI solution with diglyme above room temperature up to 387 K. The C₂ conformer is found to be more stable than C₁ by 4.7 ± 0.7 kJ mol⁻¹. Copyright © 2006 John Wiley & Sons, Ltd.     

Temperature dependence of the lifetime of Cr3+ luminescence in garnet crystals I

The lifetimes of the R-lines from the ² E level and the broad bands from the ⁴ T ₂ level of Cr³⁺ ions in various garnet crystals vary with the energy separation between the ² E and ⁴ T ₂ levels, which change systematically with the composition of host crystal. The trend of the Cr³⁺ lifetimes, as well as their temperature dependences in garnet crystals, is explained by zero-point vibration and phonon-assisted tunnelling between the ² E and ⁴ T ₂ states of Cr³⁺ ion.     

Unpolarized structure functions and the parton distributions for nucleon in an independent quark model

Considering the nucleon as consisting entirely of its valence quarks confined independently in a scalar-vector harmonic potential; unpolarized structure functions F ₁(x, μ ²) and F ₂(x, μ ²) are derived in the Bjorken limit under certain simplifying assumptions; from which valence quark distribution functions u _v(x, μ ²) and d _v(x, μ ²) are appropriately extracted satisfying the normalization constraints. QCD-evolution of these input distributions from a model scale of μ ²=0.07 GeV² to a higher Q ² scale of Q ₀ ² =15 GeV² yields xu _v(x, Q ₀ ² ) and xd _v(x, Q ₀ ² ) in good agreement with experimental data. The gluon and sea-quark distributions such as G(x, Q ₀ ² ) and q _s(x, Q ₀ ² ) are dynamically generated with a reasonable qualitative agreement with the available data; using the leading order renormalization group equations with appropriate valence-quark distributions as the input.     

Status of the theory of the hydrogen Lamb shift

The theory of the 2S _1/2-2P _1/2 Lamb shift of hydrogen is reviewed and compared to experiment. Recent corrections from radiative recoil of order α(Zα)⁵ m ² /M and pure recoil of order (Zα) ⁶ m ² /M are discussed. Contributions of order α ² (Zα) ⁵ m have been calculated from certain classes of diagrams. These are described while other as yet uncalculated terms are mentioned. The largest error in the theory is due to the uncertain measured value of the proton electromagnetic radius.     

Calculation of the probability of the 4 T 2→4 A 2 transition in luminescence spectra of the Mn4+ ion in gadolinium-gallium garnet

The ⁴ T ₂→⁴ A ₂ transition of the Mn⁴⁺ ion has been observed in the luminescence spectrum of Mn⁴⁺:Cd₃Ga₅O₁₂ upon intense laser pumping. It is shown that an increase in the intensity of the ⁴ T ₂→⁴ A ₂ transition with respect to the ² E→ ⁴ A ₂ transition in these crystals with increasing pumping power relates to the increased role of induced transitions. The intensity of this process is greater in the region where the ² E→⁴ A ₂ and ⁴ T ₂→⁴ A ₂ transition bands overlap most, which leads to an increase of the zero-phonon line of the latter transition, peaking at a wavelength of 694 nm. The rates of radiative and nonradiative recombination involving the ⁴ T ₂, ² E, and ⁴ A ₂ terms of the Mn⁴⁺ ion in gallium-gadolinium garnet (GGG) are calculated using data from luminescence spectra measured at different temperatures. The Mn⁴⁺:GGG crystal is proposed for use as an active element of lasers with continuous frequency tuning. __________ Translated from Optika i Spektroskopiya, Vol. 94, No. 4, 2003, pp. 590–596. Original Russian Text Copyright ? 2003 by Bulyarskiĭ, Zhukov, Prikhod’ko.     

Measurement of the proton structure functionF2 from the 1993 HERA data

The ZEUS detector has been used to measure the proton structure functionF ₂. During 1993 HERA collided 26.7 GeV electrons on 820 GeV protons. The data sample corresponds to an integrated luminosity of 0.54 pb^–1, representing a twenty fold increase in statistics compared to that of 1992. Results are presented for 7Q ²<>⁴ GeV² andx values as low as 3×10^–4. The rapid rise inF ₂ asx decreases observed previously is now studied in greater detail and persists forQ ² values up to 500 GeV².supported by Worldlab, Lausanne, Switzerland     

First results for the measurement of double-electron capture of 106Cd in the experiment TGV II

Present status of the experiment TGV II which is devoted to the measurement of double-beta decay of ¹⁰⁶Cd is given. The low background spectrometer TGV II is installed in the Modane Underground Laboratory and has been running from February 2005 with approx 10 grams of ¹⁰⁶Cd enriched at 75%. After an analysis of 3736 hours of experimental data the new improved half-life limit for 2νEC/EC decay of ¹⁰⁶Cd (0 _g.s. ⁺ → 0 _g.s. ⁺ ) is given as T ₁ ^2/2ν > 4.8 × 10¹⁹ years (90% CL). The search for 2νEC/EC decay of ¹⁰⁶Cd to the excited states of ¹⁰⁶Pd allows to determine the limits of the half-lives T ₁ ^2/2ν (0 _g.s. ⁺ → 2 ₁ ⁺ ) > 3.9 × 10¹⁹ years (90% CL) and T ₁ ^2/2ν (0 _g.s. ⁺ → 0 ₁ ⁺ ) > 5.8 × 10¹⁹ years (90% CL). Presented by I. Štekl at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September 26–29, 2005.     

Computational study of the decomposition mechanisms of ammonium dinitramide in the gas phase

CBS-QB3 method has been employed to determine the geometries, the vibrational frequencies of the reactants, the products and the transition states involved in intramolecular hydrogen-transfer and decomposition reactions of the free gas-phase H₃N···HN(NO₂)₂ (ADN^*). The results show that the intramolecular hydrogen-transfer reaction of ADN^* is more feasible than that of HDN. ADN^* and its hydrogen-transfer isomers ADN^*-IIa,b,c decompose along four channels to form NH₃ + HONO + 2NO (P_I), ?H + ?O₃ + N₂ + NH₃ (P_II), ?H + ?O₂ + N₂O + NH₃ (P_III), and HNO₃ + N₂O + NH₃ (P_IV), respectively. It has been found that the dominant decomposition channels are P_I and P_III. The hydrogen-transfer reaction can reduce the barrier of elimination of NO₂ and forming N₂O reactions in ADN^* and HDN. The decomposition of ADN^*-IIc to form NO₂ and N₂O is more feasible than that of the gas-phase HDN. The rate constants (k) of rate-determining step of ADN^* show that k_PI and k_PIII are higher than k_PIV and k_PII. Compared with HDN-IIc → N₂O+?H+?O₂, k_PIII of ADN^*-IIc is significantly higher than that of k^HDN-IIc. These results reveal that NH₃ (as a chaperon) has a certain influence on the decomposition mechanisms and kinetics of ADN^*.     

Influence of the electron concentration on the superconducting properties of the spinel system Li1-yTi2O4

In the spinel system Li_1-y Ti₂O₄ the Li content was reduced by oxidative extraction by means of a solution of I₂ as well as Br₂ in CH₃CN or by oxygen. The extraction is associated with a transition of Ti³⁺ to Ti⁴⁺: the system is Li_1-y Ti³⁺_1-yTi⁴⁺_1+y O₄. Consequently, with increasing y the charge carrier concentration decreases from the starting value of 0.5 electrons/Ti ion for LiTi₂O₄. The extraction proceeds in two steps. At the beginning, the Ti₂O₄ framework remains intact and the transition to superconductivity increases with decreasing charge carrier concentration to a maximal value of 13.2 K. Separated by a two-phase region for medium extraction levels for higher y values, a Li depleted material of approximate composition Li_0.3Ti₂O₄ is obtained. The crystal structure of Li_0.3Ti₂O₄ can be deduced from the original spinel lattice by a partial Ti migration from 16d to 16c and 8 a sites (space group Fd3m). Consequently, the Ti₂O₄ framework of Li_0.3Ti₂O₄ is disconnected and the material is no longer superconducting.     

Effect of photoexcitation on the electrical performance of ZnS: Mn thin-film electroluminescent structures

It is shown that the kinetics of the charge and current passing through a thin-film electroluminescent emitter, as well as the I-V characteristics of the emitter, greatly diverge under blue, red, and IR pulsed illumination with photon energies of ≈2.6, ≈1.9, and ≈1.3 eV, respectively, and a photon flux density of 4×10¹⁴–3×10¹⁵ mm⁻² s⁻¹. Results obtained indicate that, during the operation of the emitter, deep centers associated presumably with V _Zn ²⁻ zinc vacancies and V _S ⁺ and V _S ²⁺ sulfur vacancies exchange charge. These centers lie above the valence band by ≈1.1, ≤1.9, and ≤1.3 eV, respectively. Their concentrations are estimated as (3–4)×10¹⁶ cm⁻³ for V _Zn ²⁻ and V _S ⁺ and ≈1.5×10¹⁶ cm⁻³ for V _S ²⁺ . It is demonstrated that positive and negative space charges forming in the near-anode and near-cathode regions of the phosphor layer specify the electric performance of the emitters.     

The multiphoton ionization rate and the energy shift of atoms interacting with weak dichromatic fields with commensurate frequencies are simple functions of the phase difference

By implementing a time-independent, nonperturbative many-electron, many-photon theory (MEMPT), cycle-averaged complex eigenvalues were obtained for the He atom, whose real part gives the field-induced energy shift, Δ(ω ₁, F ₁;ω ₂, F ₂,ϕ), and the imaginary part is the multiphoton ionization rate, Γ(ω ₁, F ₁;ω ₂, F ₂,ϕ), where ω is the frequency, F is the field strength and ϕ is the phase difference. Through analysis and computation we show that, provided the intensities are weak, the dependence of Γ(ω ₁, F ₁;ω ₂, F ₂,ϕ) on ϕ is simple. Specifically, for odd harmonics, Γ varies linearly with cos(ϕ) whilst for even harmonics it varies linearly with cos(2ϕ). In addition, this dependence on ϕ holds for Δ(ω ₁, F ₁;ω ₂, F ₂,ϕ) as well. These relations may turn out to be applicable to other atomic systems as well, and to provide a definition of the weak field regime in the dichromatic case. When the combination of (ω ₁, F ₁) and (ω ₂, F ₂) is such that higher powers of cos(ϕ) and cos(2ϕ) become important, these rules break down and we reach the strong field regime. The herein reported results refer to Γ(ω ₁, F ₁;ω ₂, F ₂,ϕ) and Δ(ω ₁, F ₁;ω ₂, F ₂,ϕ) for He irradiated by a dichromatic ac-field consisting of the fundamental wavelength λ = 248 nm and its 2nd, 3rd and 4th higher harmonics. The intensities are in the range 1.0×10¹²-3.5×10¹⁴ W/cm², with the intensity of the harmonics being 1-2 orders of magnitude smaller. The calculations incorporated systematically electronic structure and electron correlation effects in the discrete and in the continuous spectrum, for ¹S, ¹P, ¹D, ¹F, ¹G, and ¹H two-electron states of even and odd parity. Received 9 July 2000 and Received in final form 2 November 2000     

Observation of the tensor glueball

In the reactions p-p → π ⁰ π ⁰, ηη, ηη′, in the mass region 1900–2400 MeV there are four relatively narrow resonances f ₂(1920), f ₂(2020), f ₂(2240), and f ₂(2300) and a broad one f ₂(2000). In the framework of quark combinatorics, we carry out an analysis of the decay constants for all five resonances. It is shown that the relations for the decay constants corresponding to the broad resonance f ₂(2000) → π ⁰ π ⁰, ηη, ηη′ are the same as those corresponding to a glueball. An additional argument in favor of the glueball nature of f ₂(2000) is the fact that f ₂(1920), f ₂(2020), f ₂(2240), and f ₂(2300) fit well the q-q trajectories in the (n, M ²) plane (where n is the radial quantum number), while the broad f ₂(2000) resonance turns out to be an unnecessary extra state for these trajectories. The text was submitted by the authors in English.     

Radiative transitions in the system of autoionizing levels of cesium atoms excited by electron impact

We study the energy dependences of electron excitation cross sections of the autoionizing levels (5p ⁵6s ²)² P _3/2 and (5p ⁵5d(³ P)6s)² P _3/2, as well as the autoionization cross sections of cesium atoms in the impact energy range from the excitation threshold to 600 eV. It is established that an increase in the excitation cross section of the ² P _3/2 levels (to 60% of the maximum value) and the deep minimum in the autoionization cross section observed in the energy region of 17–27 eV are caused by the predominance of the radiative decay channel for autoionizing levels with excitation thresholds above 17 eV. The high efficiency of the process is mainly related to the resonance excitation of these levels in the near-threshold energy region.