Analysis of the scattering of 46 MeV protons from Be and C

An analysis is made of the measurements of the elastic and inelastic scattering of 46 MeV protons by ³Be and ¹²C. The optical and collective models are used. There is considerable ambiguity in the optical parameters, and it was not found possible to obtain good fits to cross sections and polarizations simultaneously. Large quadrupole deformations were found for both ¹²C (β₂ ≈ 0.6) and ⁹Be(β₂ ≈ 1). The inelastic scattering from ¹²C agrees best with deformation of both real and imaginary parts of the optical potential, while ⁹Be shows a preference for real coupling. The 14.1 MeV level in ¹²C is interpreted as the 4⁺ rotational state, while the angular distribution for the 7.6 MeV 0⁺ level is well described by double quadrupole excitation via the lowest 2⁺. Interpretations are suggested for other inelastic transitions, including the excitation of spin and isospin oscillations.     

Inelastic electron scattering from He

The spectra of electrons scattered inelastically from ⁴He have been measured at incident energies from 150 MeV to 400 MeV for scattering angles from 38° to 90°. Through the use of a liquid ⁴He target, a high momentum resolution (≈0.25%) was obtained, and the 20 MeV 0⁺ state of the -particle was observed for the first time in electron scattering. The excitation energy and the total width of this state were determined and are in good agreement with the results from other experimental methods. It was found that the total disintegration cross section appears be smaller than 2(σ_p+σ_n) by more than an order of magnitude at the lowest q²(≈ 0.33 fm⁻²). In earlier work the assumption of a total cross section of 2(σ_p+σ_n) was found to be quite accurate for higher q². As a new result, the partial radiative width for the 0⁺ state is determined to be Γ_rad = 1.1±0.3 meV.     

Glueballs as bound states of massive gluons

Recent work in both lattice and continuum QCD shows that the gauge field is massive. We investigate the bound states of massive gluons with a Schrödinger equation and find M(0⁺⁺) ≈ 2.3 m, M(0⁻⁺) ≈ 2.7 m, M(2⁺⁺) ≈ 3.2 m, where m is the gluon mass; we expect from this as well as earlier work that m ≈ 500 MeV. These glueballs have widths typical of allowed hadronic decays.     

Hydrogen neutralization of dopant in p-type Ga0.47In0.53As

Diffusion of hydrogen has been performed in a series of zinc doped GaInAs layers using a RF hydrogen plasma. In highly doped (≈10¹⁹/cm³) materials, the free hole concentration decrease is accompanied by a significant increase of the hole mobility indicating a neutralization process of acceptors. Layers doped at a level of ≈10¹⁸/cm³ turn to n-type after hydrogenation. We also show that the hydrogen solubility in this material is fixed by the free hole density rather than by the hydrogen plasma conditions.     

Reversible H2 passivation of Si ≡ Si3 interface defects in (1 1 1)Si/SiO2

K-band electron spin resonance (ESR) at 4.3 K has revealed the dipole-dipole (DD) interaction effects between [1 1 1]P_b centers (^*Si ≡ Si₃ defects with unpaired sp³ hybrid [1 1 1]) at the 2 dimensional (1 1 1)Si/SiO₂ interface. This has been enabled by the perfectly reversible H₂ passivation of P_b, which affects the defect's spin state. Sequential hydrogenation at 253–353°C and degassing treatments in high vacuum at 743–835°C allowed to vary the P_b density in the range 5 × 10¹⁰ < [P_b] (1.14 ± 0.06) × 10¹³ cm^-2. With increasing [P_b] fine structure doublets are clearly resolved. It is found that (1 1 1)Si/SiO₂ interfaces, dry thermally grown at ≈920°C, naturally comprise a ^*Si ≡ Si₃ defect density — passivated or not — of 1.14 × 10¹³ cm^-2.     

Hyperon-Nucleon bound states and electroproduction of strangeness on He

The A(e, e′K⁺)YX reaction has been investigated in Hall C at Jefferson Lab. Data were taken for Q² ≈ 0.35 and 0.5 GeV² at a beam energy of 3.245 GeV for ³He, ⁴He. The missing mass spectra are fitted with Monte Carlo simulations including Λ, Σ⁰, Σ⁻ hyperon production. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for Λ-hypernuclear bound states is seen for ^3,4He targets.     

Elastic scattering of polarized deuterons from Al, Si and Ni between 7 and 11 MeV

Polarization parameters have been determined for deuteron elastic scattering from ²⁷Al, Si and ⁶⁰Ni at energies between 7 and 11 MeV and laboratory scattering angles from 30° to 135°. The vector polarization, iT₁₁, and two tensor parameters T₂₀ and T₂₂, were measured by scattering polarized and unpolarized deuterons which were obtained from a tandem accelerator. The largest polarization was |iT₁₁| ≈ 0.3 and |T₂₀| ≈ 0.2 for ²⁷Al at 11 MeV. For ⁶⁰Ni, the observed polarizations were substantially smaller. Angular distributions of the unpolarized cross section were also measured for ²⁷Al and Si. An optical-model analysis of the polarization and cross-section data was performed. The vector polarization was reproduced reasonably well by a vector spin-orbit coupling of similar strength as found for nucleon scattering. A tensor interaction appears to be needed to account for the observed tensor polarizations.     

Observation of enhanced dielectric permittivity in Bi doped BaFe12O19 ferrite

The dielectric properties of a 2.5 mol% Bi₂O₃ doped Ba-ferrite (BaFe₁₂O₁₉) have been investigated. The specimen shows a drastically enhanced (≈ 10⁵ times) permittivity (ε) through local polarization of Fe³⁺ electronic charges activated with nearby Bi³⁺ sites. The ε value also depends reasonably on thermal annealing (causes grain growth) of the samples. The specimens comprising large particle sizes (1–20 μ m) usually exhibit smaller ε values and low dielectric losses.     

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^*.     

Importance of the photo-beta process for the synthesis of “p” elements in stellar conditions

In this work, we compare positon capture and photo-beta disintegration probabilities in several stellar conditions.

We show that the second process can be neglected with regard to the first one in strongly endothermic nuclear transitions, whereas photo-beta disintegration can be competitive with positon capture and even can have a greater likelihood than the latter process in weakly endothermic and exothermic transitions.

In the range of temperature we consider here (T ≈ 10⁹ °K), it appears that the lifetime ratio τ(ph)/τ(e_c⁺) against photo-beta disintegration and positon capture is the smallest for densities in the neighbourhood of 10⁶ g/cm³.

Thus, we arrive at the conclusion that the photo-beta process can play a role in the synthesis of two “p” elements at least, ₆₂¹⁴⁴Sm and ₈₀¹⁹⁶Hg, for which the ratios τ(ph)/τ(e_c⁺) are close to 10 and 20, respectively, in the most favourable stellar conditions.     

Investigation of parity mixing in Ta and Lu by measurement of the circular polarization of γ-rays

The circular polarization of the 482 keV γ-radiation of ¹⁸¹Ta and the 343 keV γ-radiation of ¹⁷⁵Lu was measured with a Compton polarimeter. Spurious effects arising from higher order contributions of quantum electrodynamics to the Compton scattering cross section were discovered. The results for the polarization are P = − (4.1±1.3)10⁻⁶ for ¹⁸¹Ta and P = − (1.5±6.0)10⁻⁶ for ¹⁷⁵Lu. These values are corrected for instrument asymmetries, bremsstrahlung and intensity of other lines.     

Measurement of the slope parameter for the neutral pion spectrum in KL → πππ decay

The π⁰ spectrum in the K_L⁰ → 3π decay was measured using a wire chambers magnetic spectrometer. In the usual approximation, the matrix element can be expressed as: M² ≈ 1 + 2a₀(M_K/M_π²)(2T_π⁰−T_π⁰max) + a₁(M_K²/M_π⁴)(2T_π⁰−T_π⁰max)². We obtained a₀ = −0.282 ± 0.011 and a₁ consistent with zero.     

Temperature dependence of the exafs spectrum in YBa2Cu3O7−δ compounds

The temperature dependence of the extended X-ray absorption fine structure (EXAFS) is studied in the high T_c superconductors, YBa₂Cu₃O_7−δ. The measurements were done at the Cu K-edge for samples of two orthorhombic phases (T_c≈90 K and ≈58 K, respectively) and a nonsuperconducting tetragonal phase. Interatomic distances and mean square relative displacements σ² for Cu-O bonds are determined by the least squares refinement. The results indicate that values of σ² increase near T_c for both the orthorhombic samples. It is concluded that this anomalous behavior related to T_c is caused by an anomalous vibration of oxygen atoms in the Ba-O layer. Changes in the Cu-O distances from 300 to 20 K are not found.     

Analysis of hot spots in deuterium plasma focus with SSNTD

Analysis of hot spots was conducted by using two kinds of pin-hole cameras, with LR-115 detectors. Hot spots emitting positive particles from nuclear processes were located. Their locations were compared with locations emitting soft X-ray. In this experiments neutron yield was ≈10⁸ n.     

Intermediate energy proton scattering and nuclear transition densities in nickel isotopes

Using the high-resolution spectrometer SPES-I, the angular distribution of 1.047 GeV protons scattered from ⁵⁸Ni, ⁶⁰Ni, ⁶²Ni, ⁶⁴Ni have been measured in the angular range 4–18°, up to 4.8 MeV excitation energy. The data are analyzed within the framework of Glauber multiple scattering theory using a spin-dependent NN scattering amplitude. The parameters of the neutron density distributions have been determined by a χ² analysis of elastic scattering. The inelastic data corresponding to the first 2⁺ and 3⁻ states are analyzed with the collective model and an attempt has been made to extract information about the corresponding neutron transition densities.     

Direct interaction theory of production of hypernuclei by meson scattering

A calculation is made, using a direct interaction model, of the differential cross section for the scattering K⁻ +nucleus → π⁻+hypernucleus. Careful attention is paid to the normalisations in order to obtain a reliable estimate of the absolute magnitude for the process. This is of such a size (≈ 10 mb) as to merit experimental investigation.     

Towards a better understanding of O nuclear structure: Muon capture and radiative pion capture reactions

Muon capture and radiative pion capture reactions on ¹⁶O have been analysed with the aim to extract more information on the importance of higher components of the A = 16 nuclear ground and excited states. Good agreement with the experimental data for both reactions may be achieved if at least 2p2h components of the nuclear wave functions are taken into account. The positive parity excited states in ¹⁶N are shown to contribute 43 % to the radiative π⁻ capture but only ≈ 10 % to the muon capture rate.     

Radiothermoluminescence of poly(tetra fluoroethylene) and poly(ethylene terephthalate) pretreated by xenon ions

Low-temperature (77–300 K) RadioThermoLuminescence (RTL) investigations of Poly(Tetra FluoroEthylene) (PTFE) and Poly(Ethylene TerePhthalate) (PET) foils previously treated by different flux (Φ = 10⁶–10¹¹ cm⁻²) of Xenon ions with energy 1.1 MeV/nucleon have been showed an essential ion-induced changes in RTL of the both polymers under study. In PET as well as in PTFE significant changes of RTL light yield observed at the ion flux more than 10⁹ cm⁻². Variation of RTL light yield in PTFE accompanied by appearance of new TL temperature maxima on the glow curve. An existence of correlation between observed changes of molecular mobility in ion-irradiated polymer and optical (PET) and strength (PTFE) properties have been found.