A study of the S levels and the analogue levels of P by the P(He, d)S reaction

The ³¹P(³He, d)³²S reaction has been studied with high resolution at 12 MeV bombarding energy. A detailed level scheme for ³²S has been determined up to an excitation energy of 9.5 MeV revealing several previously unobserved states. The l_p values and absolute spectroscopic factors extracted from a DWBA analysis of the experimental deuteron angular distributions have provided information on the wave functions for the T = 0 states as well as for the T = 1 isobaric analogue states of ³²P. A comparison between the present data and those of previous experiments is made, and the results are discussed in terms of existing theoretical work in this mass region. Information on Coulomb displacement and symmetry energies is also extracted.     

Charge dependence of nuclear forces in ΔJ = 0, ΔT = ±1 beta decays

By assuming the validity of the conserved vector current theory, the Fermi nuclear matrix elements M_F for the beta decays of ²⁰F, ⁴¹Ar, ⁴⁴Sc, ⁵²Mn and ⁵⁶Co which violate the ΔT = 0 selection rule are calculated theoretically in the jj-coupling, shell model. In these calculations, M_F is obtained by considering a short-range, charge-dependent, internucleon potential in addition to the usual Coulomb potential. Experimental values of M_F have been obtained by measuring the asymmetry parameter A appearing in the β-γ circular polarization correlation. Comparison between the theoretical and experimental values yields the result that the deviation of nuclear forces from exact charge independence is about a few per cent, while the deviation from charge symmetry is consistent with a value an order of magnitude smaller. If the conserved vector current theory is not valid, additional contributions to the Fermi nuclear matrix elements can arise from mesonic exchange currents. It is noted that such effects could be as large as those due to charge-dependent forces and would therefore cloud the above interpretation.     

Temperature range for critical scaling behavior in YBCO thin films

The magnetic and transport properties of thin films and single crystals of YBa₂Cu₃O_7−δ are compared. For measurements on thin films, the apparent critical scaling behavior is observed to exist over a temperature range from 87 K down to the vortex-glass transition T_g = 84.2 K at 2.5 kOE and from 83 K to T_g = 70.4 K at 50 kOe. The inflection point (T_inf) in temperature dependent resistivity measurements R(T) coincides with the highest temperature at which current-voltage (I–V) characteristics are found to scale. The region between T_g and T_inf shows a behavior characteristics of thermally activated flux motion, while above T_inf I–V curves show ohmic behavior. No similar scaling region is observed in some single crystal results, supporting recent claims that the phase transition in some single crystals may not be critical in nature (of order greater than one).     

Study of Sc states with proton transfer reactions on Ca

The proton transfer reactions (d, n) and (τ, d) on ⁴²Ca have been studied. The reaction ⁴²Ca(d, n)⁴³Sc has been studied by the time-of-flight method at deuteron energies between 5.0 and 6.05 MeV. The reaction ⁴²Ca(τ, d)43Sc has been studied at 18.0 MeV with a magnetic spectrograph. Altogether 54 levels in ⁴³Sc up to an excitation energy of 6.92 MeV have been identified including states at 4.234 and 6.145 MeV which are analogues of the ground state and the 2.048 MeV state respectively in ⁴³Ca. The l-values and spectroscopic strengths have been determined for 31 transitions. Within the errors of the experiments and the DWBA analyses, the spectroscopic strengths derived from the (d, n) and the (τ, d) experiments are in agreement for both and states, i.e. there are no T-dependent discrepancies. Similar agreement is found in the strengths of the s- and d-hole transitions which reflect the degree of particle-hole impurity in the ⁴²Ca_g,s. wave function. A second state is indicated at 2.657 MeV. It appears a likely candidate for the head of a second band of 6p-3h character as proposed by Johnstone.     

Temperature and pressure dependence of NMR frequencies in ferromagnetic Heusler alloys containing cobalt and manganese

The ⁵⁹Co and ⁵⁵Mn NMR frequencies ν in Co₂MnZ (Z = Si, Ge, Sn and Ga) were measured as a function of temperature T and pressure P by the cw method. The ν/ν_4.2 value decreased faster for ⁵⁹Co than for ⁵⁵Mn with increasing T/T_C especially in Co₂MnGa, for which ∂ν/∂P was positive at 0°C in contrast to the results in other alloys.     

Remarks on stochastic non-linear birth and death models

The first part of this paper is an attempt to formulate and motivate additional work on the important problem of obtaining global bounds applicable to the controlled truncation of the paper relates specifically to the linear birth, quadratic death model. Asymptotic results are given for the first finite difference ΔT_m where T_m is the exactly known mean time to extinction starting from state m (m= 0,1,…). These results are in terms of the environmental carrying capacity n^* taken to be large. For m near zero ΔT_me^n*/(n^*)²; whereas, for m near n^*ΔT_m ≈ (π/2)^1/2/(n^*)^3/2. This indicates the vastly different time scales in those two regions of state space - with considerably slower action near extinction than near n^*.     

Investigation of light scalar resonances a0(980)/ƒ0(980) with ANKE

A program to investigate the light scalar resonances a₀(980)/ƒ₀(980) in hadronic interactions via their decay into the πη and channels has started at the ANKE spectrometer of COSY-Jülich. As the first step the reactions pp → dπ⁺X and pp → dK⁺X have been measured at two energies, T_p = 2.65 GeV and 2.83 GeV. The status of the analysis at T_p = 2.65 GeV is presented. A total cross section of about 50 nb has been determined for the reaction .     

Thermal transport properties in a He---He mixture near and below the superfluid transition

Measurements of the thermal conductivity and of X/T are reported for a ³He---⁴He mixture with a ³He mole fraction X = 0.622. At T_λ, X/T passes through a sharp peak. A comparison with the theory of Khalatnikov is presented. The relaxation times τ(T) to reach steady state conditions show qualitatively the same behaviors as X/T.     

Two separate Li ionic motions observed by Li and B NMR in xLi2S + (1 − x)B2S3 glassy fast ionic conductors

Studies of ion dynamics in the highly conductive glassy fast ionic conductor (FIC) xLi₂S + (1 − x)B₂S₃ (x = 0.65 and 0.70) were made with NMR nuclear spin lattice relaxation (NSLR) R₁(ω, T) of both mobile ⁷Li and immobile ¹¹B ions, and ⁷Li NMR line narrowing δν(T). The possible dependence of ion dynamics on the short range order structures (SRO) and the distribution of activation energies (DAE) in this highly conductive FIC was investigated. Two Gaussian DAE were employed to fit ⁷Li NSLR data, where each Gaussian DAE was correlated to a separate ¹¹B NSLR in a BS₃ and in a BS₄ group. The long range diffusion of Li ions among BS₃ groups and a seemingly localized ionic hopping motion around BS₄ group is suggested as a microscopic model for the ion dynamics in thioborate glasses, namely a ‘two channel relaxation’.     

On the rotational partition function for tetrahedral molecules

A rigorous calculation of the quantum-mechanical rotational partition function for tetrahedral XY₄ molecules yields Q_r = ( )(2I_Y + 1)⁴π ^- exp(/4), where I_Y is the spin of the Y nucleus, and ≡ Bhc/kT. This result is accurate to 1 per cent or better for all values of B and T such that < .     

NMR study of nearly itinerant antiferromagnetic Y1−xScxMn2

The NMR investigation of Y_0.97Sc_0.03Mn₂ has revealed that this compound remains paramagnetic down to 4.2 K. The nuclear spin-lattice relaxation rates, 1/T₁, of ⁵⁵Mn and ⁴⁵Sc in Y_0.97Sc_0.03Mn₂ show the T dependence as predicted from the self-consistent renormalization (SCR) theory of spin fluctuations for nearly antiferromagnetic metals.     

Pion-transfer (n, d) and (d, He) reactions leading to deeply bound pionic atoms

Theoretical studies are given on the (n, d) and (d, ³He) reactions leading to deeply bound pionic atoms in heavy nuclei of configuration [(nl)_π·j_n⁻¹]J. The cross sections for various pionic and neutron-hole configurations in the case of a ²⁰⁸Pb target are calculated at incident energies 300–1000 MeV/u by using the effective number approach and the eikonal approximation for distortion. The effective number with a pion in the 1s or 2p state and a neutron hole in the orbit peaks around the same incident energy (T_n = 600 MeV) as the elementary cross section n+n→d+π⁻, where the momentum transfer matches the angular-momentum transfer of L = 5–7. The DWIA cross section for (n,d) producing a pion in the 1s or 2p orbit at T_n = 600 MeV is found to be around 42 or 75 μb/sr, respectively. At T_n = 350 MeV, where the momentum transfer is small, quasi-substitutional states of configurations and are preferentially populated with (n, d) cross sections of 95 and 190 μb/sr, respectively. The (d, ³He) cross sections are estimated to be an order of magnitude smaller than the (n, d) cross sections. Thus, the (n, d) and (d, ³He) reactions are found to be suited for the production of deeply bound pionic atoms.     

Effective activation energy Ue(T,J,H) in textured Bi1.84Pb0.4Sr2Ca2Cu3Oy silver-clamped thick films

We have measured the resistivity of textured Bi_1.84Pb_0.4Sr₂Ca₂Cu₃O_y silver-clamped thick films as a function of temperature, current density ranging from 10 to 1×10³ A/cm² and magnetic field up to 0.3 T. We find that the effective activation energy U_e follows U_e(T,J,H)=U₀(1−T/T_p)^mln(J_c0/J)H⁻ with m=1.75 for Hab-plane and 2.5 for Hc-axis and =0.76 for Hab and 0.97 for Hc, for the current density regime above 100 A/cm², where T_p is a function of applied magnetic field and current density. This result suggests the effective activation energy U_e be correlated with the temperature, current density and magnetic field. The possible dissipative mechanisms responsible for the temperature, current density and magnetic field dependence of the effective activation energy are discussed.     

1-forms over the moduli space of irreducible connections defined by the spectrum of Dirac operators

Let (P) be the moduli space of irreducible connections of a G-principal bundle P over a closed Riemannian spin manifold M. Let D_A be the Dirac operator of M coupled to a connection A of P and f a smooth function on M. We consider a smooth variation A(u) of A with tangent vector ω and denote T_ω:= (D_A(u)−f) (u=0. The coefficients of the asymptotic expansion of trace (T_ω · e^-t(D_A−f)2) near t=0 define 1-forms a^(k)_f, K=0, 1, 2, … on (P). In this paper we calculate aa⁽⁰⁾_f, a⁽¹⁾_f, a⁽²⁾_f and study some of their properties. For instance using the 1-form a⁽²⁾_f for suitable functions f we obtain a foliation of codimension 5 of the space of G-instantons of S⁴.     

Flux creep and flux flow for thallium ceramics in a pulsed magnetic field

The resistive properties of Tl-ceramics with T_c|=0=114 K were investigated in a pulsed magnetic field (B) up to 30 T and in the temperature range of 4.2 K<T<140 K. It was shown that the character of the field dependence of the resistance differs qualitatively in high-and low-temperature regions. At low (T80K) temperatures the dynamic magnetoresistance arising in the sample is analogous to that observed earlier in LaSrCuO [1] and YBaCuO [2] ceramics. This magnetoresistance is defined by the magnetic field variation rate and leads to the appearance of a minimum at the maximum of the magnetic field pulse, i.e. at . In the region of high temperatures (80 K T<T_c) or magnetic fields (at T60K) the sample resistance rises monotonically with B increase, and dynamic resistance is not observed. In this temperature range the existence of a scaling relation is shown (here B^* and T^* meet the condition k=(B^*, T^*)/ _n(T^*)=const) for the ceramics resistance (B,T), which can be represented as . An estimate for the upper critical field B_c2(0)B_o=1030±40 T is obtained.     

The axial isoscalar neutral current from inelastic electron-nuclear scattering

Parity violating effects due to neutral currents in isoscalar 0⁺→1⁺ nuclear transitions induced by electron scattering are enhanced owing to the small isoscalar magnetic dipole strength. A polarization asymmetry of the order 10⁻⁴ is expected at q 100 MeV for the ¹²C transition to the 1⁺(T = 0) state at 12.71 MeV. It would allow to single out the (electron vector current) × (hardonic axial isoscalar current) quantum numbers and couplings of the neutral current interaction.     

The decay of Sc and V

The decays of ⁴⁸Sc and ⁴⁸V have been studied with Ge(Li) diodes, scintillation spectrometers and a double focussing beta-ray spectrometer. The 3507 keV level, from which originates the quadruple cascade (9.4±0.5)% in the ⁴⁸Sc decay, is also de-excited by a 1212 keV cross-over transition to the 2295 keV (4⁺) level and supports the assumption, that the 3507 keV level has a spin 6⁺. The first member of the reported triple cascade in the ⁴⁸V decay is shown to be a doublet of 928.9±0.7 (1.2±0.2)% and 944.3±0.5 keV (8.0±0.5)% gamma rays, both followed by the 1311.4–983.3 keV cascade. Evidence was found, that the 2421 keV (2⁺) level is excited by weak gamma rays from high-energy levels. The K/β⁺ ration in the ⁴⁸V decay is 0.69±0.05 The Q-values of ⁴⁸Sc and ⁴⁸V are calculated to be 3986±7 keV and if 4015±4 keV, respectively. The energy of the gamma ray of ⁴⁷Sc, which is present as an impurity, is 159.2±0.5 keV.     

Magnetic properties and domain structure of polycrystalline DyFe3

Magnetization σ vs. temperature T was measured from 80 to 700 K in polycrystalline DyFe₃ in a magnetic field H = 10 kOe. From σ = f(T), the Curie temperature was determined. Also, σ was measured vs. H from 0 to 70 kOe at 4.2 K. Magnetization at saturation σ₀ at 4.2 K and the magnetic moment of DyFe₃ were also determined. First observations of domain structure in DyFe₃ are reported. The mean domain with is determined in its dependence on the grain size . The magnetocrystalline anisotropy constant of polycrystalline DyFe₃ is determined as K₁ = -1.2×10⁷ erg/cm³.     

LiAl分子基态、激发态势能曲线和振动能级

利用单双激发多参考组态相互作用方法获得了LiAl分子基态X¹∑⁺及七个激发态a³∏, A¹∏, b³∑⁺, c³∑⁺, B¹∏, C¹∑⁺, d³∏的势能曲线, 通过势能曲线得到各态的平衡核间距R_e, 进而求得绝热激发能和垂直激发能.计算结果表明:c³∑⁺ 电子态是一个不稳定的排斥态, A¹∏态是一个较弱的束缚态, 其余6个电子态均为束缚态; b³∑⁺与 c³∑⁺态之间存在预解离现象; 8个电子态分别解离到两个通道, 即Li(²S)+Al(²P⁰)与Li(²P⁰)+Al(²P⁰). 接着将势能曲线拟合到Murrel-Sorbie解析势能函数形式, 据此获得各态的光谱数据:基态X¹∑⁺的平衡键长为0.2863 nm, 谐振频率为316 cm^-1, 解离能D_e为1.03 eV, 激发态a³∏, A¹∏, b³∑⁺, c³∑⁺, B¹∏, C¹∑⁺, d³∏的垂直激发能依次为0.27, 0.83, 1.18, 1.14, 1.62, 1.81, 2.00 eV; 解离能依次为1.03, 0.82, 0.26, 排斥态, 1.54, 1.10, 0.93 eV, 相应谐振频率 ω_e为339, 237, 394, 排斥态, 429, 192, 178 cm^-1. 通过求解核运动的薛定谔方程找到了J=0时 LiAl分子7个束缚电子态的振动能级和转动惯量. 关键词： LiAl 光谱常数 势能曲线 振动能级