1996 Vol. 20, No. S2
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By using a detection system combining the time-of-flight (TOF) method with the △E_E technique, the excitation functions, the dependence of the dinuclear system's energy coherence widths Γ on the product mass number A and on the product degree of freedom of neutron excess N/Z for some elements and their isotopes in the dissipative reaction 19F+51V at energies from 102.25 MeV to 109.50 MeV (in 250 keV steps) were presented and discussed for the first time.
The high spin isomer (HSI) in 144Pm was produced and separated by using the high spin isomer beam facility. Based on the measurements of γ-γ coincidence, γ-ray excitation functions, and isotropies, the decay level scheme of the HSI was established for the first time including 19 new high spin levels and 29 new γ-transitions assigned to 144Pm by this work. The HSI-γ correlation measurement indicated that the half-life of the HSI is longer than 2 μs. From the systematic comparisons and the deformed independent particle model calculations for the N=83 isotopes, the most possible particle configuration of π(1h11/22d5/2)υ(1i13/21h9/22f7/2) and the spin-parity of J*=27+ were assigned to this HSI corresponding to an oblate deformation with β=-0.18.
The in-plane and out-of-plane emission of light particles from 40Ar+197Au collisions at 25 MeV/u was studied by means of coincidence measurement of light particles with two fission fragments. An in-plane emission enhancement was observed for mid-rapidity p, d, t, α particles, indicating that a rotational effect exists in this reaction system. This enhancement becomes more obvious with the increase of mass of the particles, or with the increase of the impact parameters. It was also found that for projectile-like particles the in-plane emission is dominant.
The process e+e-→J/ψ→γ+X(JPc),X→BB (baryon and anti-baryon) is analyzed by using the helicity angular distribution method. The angular and the projection angular distribution formulas for different spin-parity of the resonance X are obtained. With these formulas, we can determine the spin of the resonance X through the analysis of the experimental data.
The anisotropy of azimuthal distributions for final state particles in center-of-mass systems where the z axis is rotated to various polar angle in the reaction plane is studied, and a method to determine the flow angle is proposed. Studying the polar angle distributions for collisions of 1.2AGeV Ar+KCl,1.2AGeV Ne+NaF,and 2.1AGeV Ne+NaF at the Bevalac streamer chamber in the coordinate systems with the z axis rotated to the flow angle, we can estimate the fraction of the anisotropic emission particles to all the final state particles and the degree of concentration around the flow direction quantitatively.
A geometrical model is proposed for the transverse energy distributions in ultra-relativistic heavy ion collisions based on the Glauber theory. The calculated distributions dσ/dET for 60 and 200 AGeV 160+197Au are in good agreement with the data of CERN NA35 Collaboration. The relation with other geometrical models is discussed briefly.
We use the RVUU model to study dynamical processes of the kaon and pion produced in heavy ion collisions. We include the nuclear medium effect on kaon and pion in the model, and simulate the pion production and kaon subthreshold production process in heavy ion collisions at 1 GeV/nucleon. The calculated results show that the attractive pion optical potential changes the final pion momentum spectrum, increasing transverse momentum spectrum at the low momentum region. At the same time, it also apparently enhances kaon abundance and modifies kaon momentum distribution. It illustrates that both kaon and pion final state dynamic processes should be considered in order to make a reasonable comment on the signals in heavy ion collisions.
A shell model calculation is carried out for nuclei with 9 ≤ A ≤ 14 and 3 ≤ Z ≤ 5. In the calculation, 8He is treated as core. The data for 24 experimental energy spectra are selected to determine the parameters of the modified surface δ interaction (MSDI) and the single-particle energies. The energy root-mean square deviation is RMS=0.72 MeV. Then the binding energies, the low-lying excited energy spectra, and the electromagnetic properties are calculated and the results are in good agreement with existing measurements in general. The micromechanism of the halo structure and the parity conversion of the 11Be are discussed in detail. This work is carried out with the shell model code OXBASH.
The macro-microscopic model is applied to study the properties of the nuclei far from stability line. Some results are obtained, e.g., proton and neutron drip line, changes of proton and neutron density distributions, and the rms radii and neutron skin thickness with isospins. The calculated results of some exotic nuclei are compared with those of relativistic mean-field approach. Brief discussions for proton radioactivity are given.
The variation of equipotential lines of interaction potential with time intuitively gives the information about the fluctuation of the potential in intermediate energy heavy ion collisions. At the early stage of collisions, the potential value in the central region of the system could be positive. The pursued irregular deformation of equipotential lines in the region, especially the appearance of the negative curvature of the equipotential lines, causes the chaotic nucleonic motion. The phase difference of the neighboring nucleons increases with time exponentially, and the phase space of nucleons therefore separates and causes the multifragmentation.
In the frame of the multichannel fission and random neck rupture model, the fragment mass, average kinetic energy distributions, and the neutron multiplicities of the neutron-induced fissions 233,235,238U are calculated covering the incident neutron energy range from thermal to 6 MeV. The theoretical results are in accord with the experimental data. The dependence of the fission channel probability on the excitation energy has been investigated.
The q-deformed nuclear magnetic moment operator is defined in terms of rank-1 tensor operator of the quantum algebra SUq(2). The results show that the q-deformation parameter depends on valence nucleon number in a major shell. The magnetic moments of odd A nuclei with only one valence nucleon outside a closed single-j shell are fitted. It shows that in most cases the results are improved in comparison with the corresponding Schmidt values.
Electron beam transverse temperatures due to electron passing through the toroid and magnetic field inhomogeneity are presented for the proposed HIRFL-CSR electron cooler, starting from motion equations of single electron in the magnetic field. Some results are given.
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