Pairing-energy coefficients of neutron-rich fragments in spallation reactions

The ratio of pairing-energy coefficient to temperature(a_p/T)of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model.A series of spallation reactions,0.5A and 1A Ge V~(208)Pb+p,1A Ge V~(238)U+p,0.5A Ge V~(136)Xe+d,0.2A,0.5A and 1A Ge V~(136)Xe+p,and~(56)Fe+p with incident energy ranging from 0.3A to 1.5A Ge V,has been analysed.An obvious odd-even staggering is shown in the fragments with small neutron excess(I≡N-Z),and in the relatively small-A fragments which have large I.The values of a_p/T for the fragments,with I from 0 to36,have been found to be in a range from-4 to 4,and most values of a_p/T fall in the range from-1 to 1.It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions.It is also concluded that the method proposed in this article is not good for fragments with A/A_s85%(where A_(s )is the mass number of the spallation system).     

Spectral line broadening and shift by collisions in an air-acetylene flame

Collisional broadenings and shifts of profiles have been investigated for the following emission lines: 5889.95 A Na, 4047.20 A K, 4226.73 A Ca, 3273.96 A Cu, and 4030.76 A Mn in an air-acetylene flame. The Lorentz widths δλ_L at half-maximum intensity, the shifts δλ_s, and the ratio η ≡δλ_L/δλ_s were determined experimentally. The values of C₆ in the Lennard-Jones (LJ) potential were calculated from a Coulomb approximation. For the LJ-potential, δλ_c,δλ_s and the repulsive constants C₁₂ were calculated from η_exp, C₆ and compared with experiments. A method is proposed for η<2.78 to obtain suitable values of the broadening parameters. We recommend calculation of the total potential function because the LJ-potential may not be suitable for all systems, particularly when η<2.78. The natural (δλ_N) and quenching (δλ_q) widths were calculated and used as correction factors.     

Gamma-ray-L-x-ray directional correlations in182W

Directional correlations between gamma radiation andL x-rays in¹⁸²W have been measured. The x-rays are emitted following the internal conversion process of the 100.1 keV 2⁺ → 0⁺ transition. The experimental results for anisotropies involving gamma radiation emitted in the 1189.0 keV transition andL x-rays are A(γ?L _l )=?0.073(27),A(γ?L _α)=?0.0102(45),A(γ?L _β)=?0.0031(35), andA(γ?L _γ)=?0.007(13). The value deduced for the coefficientU ₂(e) pertaining to the converted transition isU ₂(e)=0.52(8) in reasonable agreement with the theoretically expected value 0.410. A note is given on the use of internal conversion radial matrix elements.     

Probing hadronic polarizations with dilepton anisotropies

We investigate the production of e ⁺ e ^? pairs from p + Be and nucleus-nucleus collisions from 2 GeV/A to 200 GeV/A within a covariant transport approach and focus on the dilepton angular anisotropies as a function of the dilepton invariant mass. Whereas the low mass regime yields information about the Dalitz decays of the Δ, η and ω, above M ≈ 0.5 GeV the angular anisotropies provide additional information about the π ⁺ π ^? → ρ ⁰ → e ⁺ e ^? channel in the medium. The anisotropy coefficient is found to change its sign for M > 0.5 GeV in case of nucleus-nucleus reactions when increasing the bombarding energy from 2 GeV/A to 200 GeV/A which sheds some light on the ππ → ρ dynamics.     

On q-Laplace operator and q-harmonic polynomials

A q-Laplace operator and q-harmonic polynomials on the quantum vector space are studied. A q analog of associated spherical harmonics are constructed. They constitute an orthonormal basis of the space of q-harmonic polynomials. A q analog of separation of variables is given.     

A comparative study of the NNπ system: (I). The πd → πd, πd → NN channels

Numerical results are presented for πd → πd, πd NN observables for 290 ? T_π (MeV) ? 50. We discuss sensitivity of predictions for various input elements like the deuteron form factor, the range of the NNπ vertex and the parametrization of the background part of the P₁₁πN scattering matrix and remark on possible parallels for A(π, π) and A(π, 2N) amplitudes. A comparison is made with previously obtained results of similar scope.     

Lattice vibration analysis of cryolite A3B′X6 and elpasolite A3BB′X6 compounds. A force constant calculation of Sr2ZnTeO6

A normal coordinate treatment of crystals with general formula A₃B′X₆ and A₂BB′X₆ with cubic structure (space group F_m3m) is made with the G-F matrix method. A modified valence force field is assumed to give a set of ten force constants for calculating all fundamental vibrations in the k = 0 approximation.     

Pion-production in heavy-ion collisions at SIS energies

We investigate the production of pions in heavyion collisions in the energy range of 1–2 GeV/A. The dynamics of the nucleus-nucleus collisions is described by a set of coupled transport equations of the Boltzmann-Uehling-Uhlenbeck type for baryons and mesons. Besides theN(938) and theΔ(1232) we also take into account nucleon resonances up to masses of 1.95 GeV/c² as well asπ-,η- andρ-mesons. We study in detail the influence of the higher baryonic resonances and the 2π-production channels (NN→NNππ) on the pion spectra in comparison toπ ^? data fromAr+KCl collisions at 1.8 GeV/A andπ ⁰-data forAu+Au at 1.0GeV/A. We, furthermore, present a detailed comparison of differential pion angular distributions with the BEVALAC data forAr+KCl at 1.8 GeV/A. The general agreement obtained indicates that the overall reaction dynamics is well described by our novel transport approach.     

Eine scheinbare Abschwächung der Lokalitätsbedingung

For a hermitean, scalar, tempered fieldA(x) the locality axiom can be replaced by the following condition: For any two natural numbersn andj with 1≦j<n and for any configurationX(n, j):X ₁, ...,X _j?1,X _j ,X _j+1,X _j+2, ...X _n that is totally space-like in both orders: 1, ...,j?1,j, j+1,j+2, ...,n and 1, ...,j?,j+1,j,j + 2, ...,n there exist constants α(n,j)>2,C(X(n, j))>0,h(X(n, j))>0 such that with \(x_k = X_k \sqrt { - x^2 } \) : $$\begin{gathered} |\langle A(x_1 ) \ldots A(x_{j - 1} )[A(x_j ), A(x_{j + 1} )] A(x_{j + 2} ) \ldots A(x_n )\rangle |< \hfill \\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,< C(X(n, j)) exp\{ - h(X(n, j))\sqrt { - x^2 } ^{\alpha (n, j)} \} \hfill \\ \end{gathered} $$ for ?x ²>1.     

Sur une Valeur propre d'un Operateur

The studied eigenvalue is the smallest one of the operator: $$H_\mu = \mu A* + i\lambda A*(A + A*)A$$ in the orthogonal complement of the vacuum whereA* andA are the creation and annihilation operators. Call this eigenvalueE(μ) as attention is focused on the dependence on μ. This eigenvalue exists and is a positive number for positive values of μ. Using the fact that the inverse ofH _μ is a positive operator, it is proved thatE extends to a positive, increasing, analytic function on the whole real line. In particular,E(0)≠0, contrary to what might have been expected from the fact thatA*(A+A*)A is formally self-adjoint.     

SAXS study of the structure of amorphous Fe75TM5B20 (TM  Ti,V, Cr,Mn, Fe,Co, Ni)

A SAXS study was undertaken on Fe₇₅TM₅B₂₀ amorphous alloys (TM  Ti, V, Cr, Mn, Fe, Co, Ni) to prove the effects of the substituting metals on structural homogeneity of the systems. A density-density correlation extending up to 20 Å belongs to Fe-, Ni- and Co-containing alloys whereas the absence of a medium-range order characterizes the texture of the remaining alloys. A net correspondence was found between these structural conditions and the isothermal behavior of the resistivity.     

Electron states on the (111) surface of copper

A calculation of electronic states at the (111)-surface of Cu in the energy region around E_F is presented. The calculation is based on the empirical pseudopotential method. A proper position of an abrupt potential barrier ensures overall charge neutrality. A surface state is found at 0.13 eV below E_F, being localized midway between atomic layers. The effective mass of the associate bands is 0.39m_e. Our results are in good agreement with directional photoemission data.     

Properties of disordered Mo3Ge thin films with A15 structure

Heavy ion irradiation of A15 Mo₃Ge with the low transition temperature T_c = 1.45 K raises T_c to ? 6 K. For the first time in A15 compounds a T_c degradation (≈ 3 K) after having passed through a maximum is observed until near 3.5 K the saturation value is reached. The effects on T_c are interpreted by variations of the deduced (H'_c2, ?) density of states at the Fermi level. This picture consistently explains the T_c degradation of the high-T_c A15 compounds.     

Heavy particles and the ϱ parameter in the standard model

A new formalism is presented for the calculation of the contribution δ? to ? = M_w²/M_z²cos²θ_w from heavy particles transforming according to arbitrary representations of SU(2) × U(1). A conjecture for the necessary and sufficient conditions that δ??0 for all values of masses and mixing angles within a particular multiplet is formulated. A number of examples are given (all consistent with the conjecture) and the significance of improved knowledge of ? vis à vis the possible existence of undiscovered heavy particles discussed.     

s- and p-wave neutron spectroscopy Xf(i). Intermediate structure in the 28Si + n reaction: R-matrix interpretation of experimental data

A multilevel R-matrix analysis of Si neutron cross-section data measured at NBS has been performed up to about 4.5 MeV neutron energy. Only a small fraction of the p- and s-wave s.p. strength is observed, but both exhibit local concentrations of strength indicative of doorway structure around 1 and 0.2 MeV, respectively. Besides the well-known 180 keV, strong, $\text{1}\text{2}{}^{\mathrm{+}}$ resonance, the s-wave resonance structure is of moderate strength and widely distributed. The f- and d-wave assignments are not unambiguous, but J > 3/2 resonances show strong signs of intermediate structure for d-waves. A possible correlation between neutron and gamma decay channels and the connection between the states observed in (n, n), (d, p), (n, γ), and (γ, n) channels is discussed. A coreparticle doorway interpretation for s and p- waves is presented.     

Incomplete relaxation and plasmon formation in the K emission band of copper

A method of calculating the effect of self-absorption in X-ray emission spectra and which is suitable for non-adiabatic excitation processes is presented. The Fermi-level E_F and the “true” profile of the electron-excited (20–40keV) CuKβ_2,5 band are determined. A deviation from the calvulated one-electron spectrum in the energy interval [-12 eV, -7 eV] below E_F is interpreted as a result of plasmon formation and Auger broadening. A pronounced disagreement is found also in the range [-1 eV, + 10eV]. Above E_F, a part of the intensity may be due to incomplete electron relaxation.     

Creation of spin-oriented 2P excitons in CdS by two-photon magneto-absorption

We report experimental results on the creation of 2P excitons in CdS by the two-photon magneto-absorption process involving a simultaneous absorption of visible and infrared photons. For a magnetic field parallel to the c axis and particularly for a visible beam propagating along the c axis, spin-oriented 2P (A) excitons are created from the A (Γ₉) valence band. We explain these results on the basis of the main contribution of the 1SΓ₅ (A) exciton intermediate state.     

On the possibility of superconductivity in a MgB2 compound

A concept of strong interaction in a single unit cell is used to predict Cooper instability in a system with hopping between main-group cations and anions. A phase diagram of ferromagnetic ordering is constructed for different degrees of (n _p )p ⁶-and (n _s )s ²-shell filling in main-group elements.