Dielectric properties and phase transitions in alkali cyanides and cyanospinels under the influence of hydrostatic pressure

The effect of hydrostatic pressure p on the low-frequency dielectric constant ? has been investigated for selected cyanides (NaCN, KCN) and cyanospinels [K₂M(CN)₄ with M = Zn, Cd, Hg and Rb₂Zn(CN)₄] for pressures up to 7 kbar In the low-pressure region (decreases monotomcally resulting in negative first-order pressure denvatives of the dielectric constant The second- and third-order pressure derivatives, however, proved to be positive in most cases Using the dielectric constant as a very sensitive probe we observed phase transitions from the cubic low-pressure phase to an orthorhombic (NaCN) resp trigonal (cyanospinels) high-pressure phase at the following transition pressures (for 293.2 K) 2 260 kbar for NaCN, 1 438 kbar for K₂Hg(CN)₄, 2 660 kbar for K₂Cd(CN)₄, 3 318 kbar for K₂Zn(CN)₄ and 0.690 kbar for Rb₂Zn(CN)₄ The transition temperature T_c, was found to increase strictly linear with pressure between 290 and 340 K at a rate of dT_c/dp = 120 2 and 105 3 Kkbar^?1 for K₂Zn(CN)₄ and K₂Cd(CN)₄, respectively.     

Microwave Spectrum,Nuclear Quadrupole Coupling Constants,and Structure of Bromodifluoromethane

The microwave spectrum of bromodifluoromethane, CHBrF₂(Halon 1201) has been studied for the first time from 7 to 40 GHz. A least-squares analysis of the observedc-type transition frequencies gave rotational and centrifugal distortion constants and components of the bromine nuclear quadrupole coupling constant tensor in the principal axes system as follows:A= 10199.7186(62) MHz,B= 2903.4150(26) MHz,C= 2360.1521(23) MHz, Δ_J= 0.660(14) kHz, Δ_JK= 2.87(11) kHz, Δ_K= 8.95 kHz, δ_J= 0.1344(24) kHz, δ_K= 3.22(15) kHz, χ_aa= 521.281(92) MHz, χ_bb− χ_cc= −38.32(9) MHz, and |χ_ac| = 187.1(26) MHz for the⁷⁹Br species;A= 10199.5567(54) MHz,B= 2876.5588(20) MHz,C= 2342.3796(18) MHz, Δ_J= 0.652(12) kHz, Δ_JK= 2.77(9) kHz, Δ_K= 8.21(61) kHz, δ_J= 0.1300(19) kHz, δ_K= 2.97(13) kHz, χ_aa= 435.61(10) MHz, χ_bb− χ_cc= −32.08(8) MHz, and |χ_ac| = 148.5(29) MHz for the⁸¹Br species. The structural parameters are calculated from all these rotational constants and the electronic properties of the carbon–bromine bond in bromodifluoromethane are evaluated from the observed nuclear quadrupole coupling constants. These molecular properties are compared with those of other related molecules.     

Precision measurements of the nuclear magnetic dipole moments of6Li,7Li,23Na,39K and41K

Using the atomic beam magnetic resonance method and using the technique of separated oscillatory fields in combination with the triple resonance method the ratiosg _I /g _J of the stable alkali isotopes Li, Na and K in the²S_1/2-ground state have been measured at magnetic fields of about 3 kOe. Frequency shifts analogous to the Bloch-Siegert-shift, expected from theory, were observed and eliminated by extrapolation to vanishing rf-field strength. The results, uncorrected for atomic diamagnetism, are:⁶Li:g _I /g _J =?0.22356978(10)·10^{?3 7}Li:g _I /g _J =?0.59042719(10)·10^{?3 23}Na:g _I /g _J =?0.40184406(40)·10^{?3 39}K:g _I /g _J =?0.07088613 (6)·10^{?3 41}K:g _I /g _J =?0.03890837 (4)·10^?3 Furthermore, the hyperfine structure splitting constants in the² S _1/2-ground states have been determined. Using the most precise absoluteg _J -values available so far one can calculate absolute values for the uncorrectedg _I - factors. The results are:Δν/MHz ?g _I·10^{3 6}Li: 228.2052590(30) 0.4476540 (3)⁷Li: 803.5040866(10) 1.1822130 (6)²³Na: 1771.6261288(10) 0.8046108 (8)³⁹K: 461.7197202(14) 0.14193489(12)⁴¹K: 254.0138720(20) 0.07790600 (8) By comparing the absoluteg _I - factors with measurements received by the NMR-method, the chemical shifts of the NMR-frequencies caused by the hydrate surrounding of the alkali ions in the NMR-probe are determined.     

Charged Bottomonium-Like Structures Z b (10610) and Z b (10650)

The observation of two charged bottomonium-like structures Z _b (10610) and Z _b (10650) has stimulated extensive studies of the properties of Z _b (10610) and Z _b (10650). In this talk, we briefly introduce the research status of Z _b (10610) and Z _b (10650) combined with our theoretical progress.     

Multigap superconductivity in doped p-type cuprates

Andreev and tunneling spectroscopy studies of Bi₂Sr₂Ca _{n ? 1}Cu _n O_{2n + 4 + δ}, HgBa₂Ca _{n ? 1}Cu _n O_{2n + 2 + δ} and Tl₂Ba₂Ca _{n ? 1}Cu_{2n + 4 + δ} have shown that superconductivity in single-layer (n = 1) and two-layer (n = 2) phases has a single-gap character. Qualitatively different results were obtained for three-layer phases. In doped p-type Hg-1223, Bi-2223, and Tl-2223 samples two (or three) superconducting gaps were observed. The existence of multigap superconductivity in superconducting cuprates with n ≥ 3 is explained by a difference in doping levels of outer (OP) and internal (IP) CuO₂ planes.     

High pressure study of BaPb0.7Bi0.3O3 films

The resistance R, the superconducting transition temperature T_c and the energy gap Δ(T) have been measured on the BaPb_0.7Bi_0.3O₃ films up to 14 kbar. We have found that up to 14 kbar: (1) pressure suppresses T_c and Δ(T) while enhances R, (2) the value of 2Δ(0)/kT_c is 3.8±0.1, independent of pressure, and (3) the Δ(T)/Δ(0) varies with T/T_c in a BCS fashion but only for T/T_c<0.75 and independent of pressure. The results show that BaPb_1?xBi_xO₃ is a weak-coupling superconductor, but fail to provide information about the cause for the high T_c of the compound.     

A fresh look at η 2(1645), η 2(1870), η 2(2030) and f 2(1910) in \bar{p}p \to \eta \pi ^{0}\pi ^{0}\pi ^{0}

There is a large discrepancy between results of Crystal Barrel and WA102 for the branching ratio R=BR[η ₂(1870)→a ₂(1320)π]/BR[η ₂(1870)→f ₂(1270)η]. An extensive re-analysis of the Crystal Barrel data redetermines branching ratios for decays of η ₂(1870), η ₂(1645), η ₂(2030) and f ₂(1910). This re-analysis confirms a small value for R of 1.60±0.39, inconsistent with the value 20.4±6.6 of WA102. The likely origin of the discrepancy is that the WA102 data contain a strong f ₂(1910)→a ₂ π signal as well as η ₂(1870). There is strong evidence that the η ₂(1870) has resonant phase variation. A peak in f ₂(1270)a ₀(980) confirms closely the parameters of the a ₂(2255) resonance observed previously. A peak in η ₂(2030)π is interpreted naturally in terms of π ₂(2245) with reduced errors for mass and width M=2285±20(stat)±25(syst) MeV, Γ=250±20(stat)±25(syst) MeV.     

SU(3) lattice Monte Carlo calculation of the glueball mass spectrum

We have calculated the glueball masses of various spins and parities in SU(3) gauge theory. Our first results give m_M(0⁺⁺)=(3.6±0.2)Λ_mom, m_E(0⁺⁺)=(4.3±0.3)Λ_mom, m(0^?+)=(7.2_?0.9^+1.6)Λ_mom, m_M(2⁺⁺)=(8.1±1.1)Λ_mom and m_E(2⁺⁺)=(8.3_?1.0^+1.6)Λ_mom as well as information on the glueball wave functions.     

Phase transitions at high pressure in the fullerene C60 molecular donor-acceptor complex {Hg(dedtc)2}2 · C60

Raman spectra of crystals of the molecular fullerene C₆₀ donor-acceptor complex {Hg(dedtc)₂}₂ · C₆₀ (fullerene with mercury diethyldithiocarbamate) have been measured at a pressure up to 8.4 GPa and at room temperature. A phase transition has been revealed in the pressure range of 1.2–2.0 GPa, which is accompanied by a splitting of the degenerate intramolecular phonon modes H _g (1)-H _g (4) and H _g (7)-H _g (8), as well as by a softening of the H _g (2) mode of the fullerene C₆₀. As the pressure further increases to the maximum value, the intensity of the bands varies smoothly. A decrease in the pressure leads to the reverse transition to the initial state at 1.2 GPa. The splitting of the degenerate modes H _g (1)-H _g (8) and the softening of the H _g (2) modes resemble their behavior in the formation of dimers in fullerite crystals and indicate the possible formation of dimers in two-dimensional fullerene layers under hydrostatic compression of the {Hg(dedtc)₂}₂ · C₆₀ complex.     

3nj coefficients of u q(2) and multiple basic hypergeometric series

Triple-sum formulas for 9j coefficients and multiple-sum expressions [with five or four separate sums of the _p+1 F _p(1) or _p+1 φ _p type, p=2, 3, 4] for the 12j coefficients of both kinds (with or without braiding) of the SU(2) group and the quantum algebra u _q(2) are derived, eliminating sums over the j type parameters [q generalizations of the very well poised (Dougall’s type) hypergeometric ₄ F ₃(?1), ₅ F ₄(1), and ₆ F ₅(?1) series] from their expansions in terms of q-6j coefficients. The rearrangements of the derived formulas for generic and stretched q-9j coefficients (related to the q versions of some Kampé de Fériet series) are discussed, as well as the different versions of stretched and doubly stretched q-12j coefficients.     

Fermion mass hierarchy based onN=8 supergravity

A possible mechanism is proposed to realize fermion mass hierarchy based on the superunification model of Ellis et al. In addition to the usual fermion (F)—Higgs (B) coupling, “non-renormalizable” interactions such as(1/(M _p ) ⁿ )(F) ² (B) ⁿ⁺¹ are introduced. It is assumed that three kinds of Higgs scalars respectively develop v.e.v. of orderM _P ,M _X andM _W , corresponding to the symmetry breaking pattern ofSU(8)→SU(5)→SU(3)×SU(3)×U(1)→SU(3)×U(1). As a result, fermions acquire their masses of orderM _w ,M _W (M _X /M _P) andM _W (M _X /M _P )². An example of the model is presented which shows nice feature of hierarchical mass patterns.     

Hyperfine structure measurements in the ground states5 F 5,5 F 4,5 F 3 and5F2 of99Ru and101Ru with the atomic beam magnetic resonance method

The hyperfine structure of the four lowest levels⁵ F _{5, 4, 3, 2} of the⁵ F ground state multiplet arising from the configuration 4d ⁷ 5s in⁹⁹Ru and¹⁰¹Ru has been studied by the atomic — beam magnetic — resonance technique. After applying corrections due to the effects of off-diagonal hyperfine mixing we obtain the following multipole interaction constants:⁹⁹Ru:A(⁵ F ₅)=?204.5514(33) MHzB(⁵ F ₅)=27.281 (62) MHzA ⁵ F ₄=?163.6845(36) MHzB(⁵ F ₄)=17.455(52) MHzA ⁵ F ₃=?135.0294(37) MHzB(⁵ F ₃)=10.164(50) MHzA(⁵ F ₂)=? 82.5325(27) MHzB(⁵ F ₂)=5.457(22) MHz¹⁰¹Ru:A(⁵ F ₅)=?229.2881(33) MHzB(⁵ F ₅)=158.934(62) MHzA(⁵ F ₄)=?183.4744(36) MHzB(⁵ F ₄)=101.799(52) MHzA(⁵ F ₃)=?151.3502(38) MHzB(⁵ F ₃)=59.323(50) MHzA(⁵ F ₂)=?92.4974(27) MHzB(⁵ F ₂)=31.869(23) MHz. The magnetic dipole and the electric quadrupole moments of the⁹⁹Ru and¹⁰¹Ru nuclear ground states as calculated from these constants are the following:μ _I (⁹⁹Ru)=?0.594(119) nmQ(⁹⁹Ru)=0.077 (15) barnsμ _I (¹⁰¹Ru)=?0.666(133)nmQ(¹⁰¹Ru)=0.45 (9) barns. From measurements of the Zeeman effect in the even isotope¹⁰²Ru we find the followingg _J -factors for the⁵ F ground multiplet:g _J (⁵ F ₅)=1.397741(20)g _J (⁵ F ₄)=1.347604(20)g _J (⁵ F ₃)=1.248988(20)g _J (⁵ F ₂)=1.001120(3).     

On the surface energy of crystals of inert gases

The dependences of the specific surface energy (σ) and its isochoric temperature derivative (?σ/?T) _V on the degree of compression (V/V ₀) of the crystal are calculated on the basis of the Mie-Lennard-Jones pair potential of interatomic interaction. The calculations are performed for all face-centered cubic crystals of inert gases (from Ne to Rn) to the degree of compression V/V ₀ = 0.016 along three isotherms: 1K, T _m and 300 K, where T _m is the melting temperature at zero pressure (V/V ₀ = 1). The activation processes such as the creation of vacancies and self-diffusion are taken into account in the calculations. It is shown that the isotherm σ(V/V ₀) reaching its maximum at (V/V ₀)_max sharply decreases upon further compression. The surface energy becomes negative (σ(V/V ₀) _fr =0) at V/V ₀ ≤ (V/V ₀) _fr < (V/V ₀)_max which should stimulate the process of crystal fragmentation, i.e., an increase in the specific (per atom) intercrystallite surface. It is shown that at high temperatures the condition of fragmentation holds in the crystal in the case of uniform tension, but it is already in the region of the liquid phase. The values of σ, (?σ/?T) _V , the vacancy concentration and the fraction of the diffusion atoms are estimated at the points: V/V ₀ = 1, (V/V ₀)_max and (V/V ₀) _fr at 1 K, Tm and 300 K. The size evolution of the surface and activation parameters is studied using neon as an example.     

Anomalous X-ray scattering studies on superionic glassy (As2Se3)-(AgX) systems (X = halides)

Anomalous X-ray scattering experiments for glassy room-temperature superionic conductors (As₂Se₃)_0.4 (AgI)_0.6 and (As₂Se₃)_0.4(AgBr)_0.6 were performed close to the As, Se, Ag, and Br K edges using a third-generation synchrotron radiation facility, ESRF. The differential structure factors, Δ_iS(Q), were obtained from detailed analyses, indicating that Δ_AsS(Q) and Δ_SeS(Q) of both the glassy superionic semiconductors are similar to those of glassy As₂ Se₃ except the prepeak in Δ_SeS(Q). The Δ_AgS(Q) spectrum of (As₂Se₃)_0.4 (AgI)_0.6 looks molten salt-like. However, the Δ_Ag S(Q) of (As₂Se₃)_0.4(AgBr)_0.6 glass have quite different features from that of (As₂Se₃)_0.4 (AgI)_0.6 glass in the low Q range, and the Δ_BrS(Q) has even a pre-shoulder around 13 nm^? 1 unlike molten salts. In the differential pair distribution functions Δ_ig(r) obtained from the Fourier transforms of Δ_iS(Q), the first peaks of Δ_Asg(r) and Δ_Seg(r) show no correlation with those of Δ_Agg(r) and Δ_Brg(r), and vice versa. From these results, it can be concluded that a pseudo-binary mixture of the As₂Se₃ network matrix and AgX-related ionic conduction pathways is a good structural model for these superionic glasses. Differences between the AgBr- and AgI mixtures were found in the second-neighbor structures around the Ag atoms, which may reflect those in the crystal structures of the AgX salts.     

Infrared spectrum of hydrogen in the condensed phase with high-sensitivity spectrometers: Experiments with a 0.04-cm−1 Fourier transform spectrometer in the range 1.5–12 μm

The infrared spectrum of solid and liquid hydrogen was recorded using a Fourier spectrometer. The pure rotational U transitions, U₀(0) in solid para hydrogen and U₀(1) in solid normal hydrogen, with the accompanying phonon branches were observed for the first time. In addition, the rotational double transitions S₀(0) + S₀(1) and S₀(1) + S₀(1) were identified. The identifications of these transitions are based on positions calculated by making use of gas phase molecular constants. In the liquid the double transitions are preserved but the single transitions U₀(0) and U₀(1) are entirely absent. The region of Q_1←0(J) reveals structure which has not been reported before. Its interpretation is presented.     

Investigation of hybrid states in the VES experiment at the Institute for High Energy Physics (Protvino)

Experimental investigations of candidates for hybrid mesons in the VES experiment at the Institute for High Energy Physics (Protvino) are surveyed. The data in question concern π ₁ (1400) characterized by the exotic quantum numbers of J ^PC = 1^?+ and observed in the ηπ ^? final state; JPC = 1^?+ π ₁ (1600) in the ηπ ^?, b ₁ (1235)π, and f ₁(1285)π ^? final states; and J _PC = 0^?+ π(1800) in the f ₀(980)π ^?, f ₀(1300)π ^?, f ₀(1500)π ^?, and a ₀ ^? (980)η final states. New results are given along with data published previously.     

Measurement of the semileptonic branching fraction of inclusive b baryon decays to Λ

We present the first measurement of the ratio R _Λl defined as R _Λl = BR(Λ _b → ΛlX)/BR(Λ _b → ΛX) where Λ _b denotes all weakly decaying b baryons and l represents the average of electrons and muons. Using all hadronic Z⁰ decay events collected with the OPAL detector near the Z⁰ resonance, we measure R _Λl = (7.0 ± 1.2 ± 0.7)%. We also measure f(b → Λ _b) · BR(Λ _b → Λ X) = (3.93 ± 0.46 ± 0.37)%, f(b → B) · BR(B → Λ X) = (1.94 ± 0.28 ± 0.24)%, and BR(b → ΛX) = (5.87 ± 0.46 ± 0.48)%. In all cases, the uncertainties shown are statistical and systematic, respectively.     

A supersymmetricSU(5)×U(1) model with natural gauge hierarchy

We present a supersymmetricSU(5)×U(1) model. This model has the following features. The gauge hierarchy is naturally generated by the quadratically divergent nature of the Fayet-IliopoulosD term. TheSU(5)×U(1) gauge symmetry breaks uniquely intoSU(3) _W ×SU(2) _c ×U(1) _y at an energy scale of 10^17–18GeV. The non-vanishing vacuum expectation value of an auxiliary field component ofU(1) gauge vector multiplet induces the breaking ofSU(2) _W ×U(1) _y . It gives a mass of 10^2–3GeV to scalar quarks and scalar leptons at the tree level. The renormalization group analysis shows that the color fine structure constant α _C (M _W ) becomes somewhat small and the Weinberg angle sin²θ _W (M _W ) somewhat too large in a simple version of the model.     

Neutron diffraction studies of the magnetic ordering in the rare earth compounds TbNi2Si2, HoCo2Si2 and TbCo2Si2

Neutron diffraction studies and magnetic measurements on the compounds TbNi₂Si₂ (1), HoCo₂Si₂ (2) and TbCo₂Si₂ (3) revealed a collinear antiferromagnetic order below T_N = 10 ± 1 K (1), T_N = 13 ± 1 K (2) and T_N = 30 ± 2 K (3) with the rare earths moments oriented along the c-axis [m₀ = 8.8 ± 0.2 μ_B (1), m₀ = 8.1 ± 0.2 μ_B (2), m₀ = 8.8 ± 0.2 μ_B (3)] and the corresponding wavevector are $\text{k}\text{= [}\text{1}\text{2}\text{1}\text{2}\text{0] (1)}\text{and}\text{k}\text{= [ 0 0 1] (2) (3)}$. The magnetic structure of the compounds HoCo₂Si₂ and TbCo₂Si₂ consists of ferromagnetic layers perpendicular to the c-axis coupled antiferromagnetically (+?+?) while for TbNi₂Si₂ the ordering within (0 0 1) plane is antiferromagnetic and the planes (0 0 1) are indeed decoupled.     

Concurrent changes of crystallographic and Mössbauer effect parameters at the high-spin(5T2) ⤥ low-spin(1A1) transition in compounds of iron (II)

Distinct and different X-ray diffraction patterns are found for the ⁵T₂ and ¹A₁ phases at the high-spin(⁵T₂) ? low-spin(¹A₁) transition in Fe(bt)₂(NCS)₂ (I) and Fe(phy)₂(ClO₄)₂ (II) (bt = 2,2′-bi-2-thiazoline; phy = 1,10-phenanthroline-2-carbaldehydephenylhydrazone). The peak profiles show the same temperature dependence and the same hysteresis behaviour as the ⁵T₂ and ¹A₁ fractions determined on the basis of Mössbauer effect or magnetism. At the transition temperature T_c, both phases are coexistent.