No abstract available

[en] For the first time a comprehensive level and decay scheme has been obtained for a T=(5/2) nucleus in the s-d shell (²⁷Na) by using a radioactive beam and target. Particle-γ and p-γ-γ coincidences were measured following the ¹⁴C(¹⁴C,pγ)²⁷Na reaction at E_lab=22 MeV. The results do not support an inversion of the 2s_1/2 and 1d_5/2 orbitals, as previously proposed for T_z≥3, but they do suggest an increased N=16 gap between the 2s_1/2 and 1d_3/2 orbitals due to the neutron excess. A consistent interpretation of the level scheme in terms of the s-d shell model using the USD Hamiltonian is possible below 4 MeV, but differences increase at higher excitation energies. Another interpretation is that the influences of both the p_1/2 and f_7/2 intruder orbitals increase simultaneously with increasing T, an effect not included in the USD Hamiltonian

[en] The problem of electron-beam propagation in inhomogeneous solar wind is intimately related to the solar type II and/or type III radio bursts. Many scientists have addressed this issue in the past by means of quasi-linear theory, but in order to fully characterize the nonlinear dynamics, one must employ weak-turbulence theory. Available numerical solutions of the weak-turbulence theory either rely on only one nonlinear process (either decay or scattering), or when both nonlinear terms are included, the inhomogeneity effect is generally ignored. The present paper reports the full solution of weak-turbulence theory that includes both decay and scattering processes, and also incorporating the effects of density gradient. It is found that the quasi-linear effect sufficiently accounts for the primary Langmuir waves, but to properly characterize the back-scattered Langmuir wave, which is important for eventual radiation generation, it is found that both nonlinear decay and scattering processes make comparable contributions. Such a finding may be important in the quantitative analysis of the plasma emission process with application to solar type II and/or type III radio bursts.

[en] The ¹⁴C(¹⁴C, d) reaction at 22 MeV was used to study T_z=2 ²⁶Na. Charged particles were detected with a Si detector telescope at 0 deg., and γ transitions in coincidence were detected with an array of three Compton-suppressed 'clover' detectors and seven Compton-suppressed single Ge crystals. The Deuteron-γ and d-γ-γ coincidence data were analyzed to study the structure of ²⁶Na. New levels were found, and precise energies and γ-decay patterns were determined for many states previously observed in charge-exchange reactions. Candidates were observed for the 1⁺ state missing in β decay. Mixing ratios were determined for some γ transitions from angular distribution information. There is reasonable agreement with the model based on the universal s-d shell (USD) interaction

[en] The statistical mechanical reformulation of weak turbulence theory for unmagnetized plasmas including fully electromagnetic effects was carried out by Yoon [Phys. Plasmas 13, 022302 (2006)]. However, the wave kinetic equation for the transverse wave ignores the nonlinear three-wave interaction that involves two transverse waves and a Langmuir wave, the incoherent analogue of the so-called Raman scattering process, which may account for the third and higher-harmonic plasma emissions. The present paper extends the previous formalism by including such a term.

No abstract available

[en] Excited states in ²⁰O were populated in the reaction ¹⁰Be(¹⁴C,α) at Florida State University (FSU). Charged particles were detected with a particle telescope consisting of 4 annularly segmented Si surface barrier detectors and γ radiation was detected with the FSU γ detector array. Five new states were observed below 6 MeV from the α-γ and α-γ-γ coincidence data. Shell model calculations suggest that most of the newly observed states are core-excited 1p-1h excitations across the N=Z=8 shell gap. Comparisons between experimental data and calculations for the neutron-rich O and F isotopes imply a steady reduction of the p-sd shell gap as neutrons are added

[en] In a recently developed nonlinear theory of Buneman instability, a simplifying assumption of self-similarity was imposed for the electron distribution function, based upon which, a set of moment kinetic equations was derived and solved together with nonlinear wave kinetic equation [P. H. Yoon and T. Umeda, Phys. Plasmas 17, 112317 (2010)]. It was found that the theoretical result compared reasonably against one-dimensional electrostatic Vlasov simulation. In spite of this success, however, the simulated distribution deviated appreciably from the assumed self-similar form during the late stages of nonlinear evolution. In order to rectify this shortcoming, in this paper, the distribution function is computed on the basis of rigorous velocity space diffusion equation. A novel theoretical scheme is developed so that both the quasilinear particle diffusion equation and the adiabatic dispersion relation can be solved for an arbitrary particle distribution function. Comparison with Vlasov simulation over relatively early quasilinear phase of the instability shows a reasonable agreement, despite the fact that quasilinear theory lacks coherent nonlinear effects as well as mode-mode coupling effects.

[en] In this paper an electromagnetic particle code is used to investigate the spontaneous thermal emission. Specifically we perform particle-in-cell simulations employing a non-relativistic isotropic Maxwellian particle distribution to show that thermal fluctuations are related to the origin of spontaneous magnetic field fluctuation. These thermal fluctuations can become seed for further amplification mechanisms and thus be considered at the origin of the cosmological magnetic field, at microgauss levels. Our numerical results are in accordance with theoretical results presented in the literature

[en] The ¹⁴C+α decay of ¹⁸O has been studied via the ¹⁴C(¹⁸O,¹⁴Cα)¹⁴C reaction at 102 MeV. The excitation energy of the decaying ¹⁸O resonant particle has been determined following the coincident detection of the correlated ¹⁴C and α particles. A study of the angular correlations of the breakup fragments has allowed the spins of the decaying states to be investigated. The data provide evidence that a quasimolecular rotational band, identified by enhanced α decay, is observed in the reaction. Evidence is also presented for the ¹⁸O+α decay of ²²Ne