579 research outputs found

    Energy Dependence of Total Cross Sections for Reactions with 4, 6he, 6, 7, 9li Nuclei

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    The paper presents the results of measurement of the total cross sections for reactions 4,6He + Si and 6,7,9Li + Si in the beam energy range 5−50 A⋅MeV. The enhancements of the total cross sections for reaction 6He + Si compared with reaction 4He + Si, and 9Li + Si compared with reactions 6,7Li + Si have been observed. The performed microscopic analysis of total cross sections for reactions 6He + Si and 9Li + Si based on numerical solution of the time-dependent Schrödinger equation for external neutrons of projectile nuclei 6He and 9Li yielded good agreement with experimental data

    Study of internal structures of 9,10Be and 10B in scattering of 4He from 9Be

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    A study of inelastic scattering and single-particle transfer reactions was performed by an alpha beam at 63 MeV on a 9$Be target. Angular distributions of the differential cross sections for the 9Be(4He,4He')9Be*, 9Be(4He,3He)10Be and 9Be(4He,t)10B reactions were measured. Experimental angular distributions of the differential cross sections for the ground state and a few low-lying states were analyzed in the framework of the optical model, coupled channels and distorted-wave Born approximation. An analysis of the obtained spectroscopic factors was performed.Comment: 16 pages, 7 figures, 3 tables, regular paper, mispritns are corrected in new versio

    Parity Inversion And Different Properties of Be11 halo Nuclei

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    The recent developments of radioactive nuclear beams has opened up the possibility of exploring a wide variety of nuclei far from the valley of beta-stability. Of late several theoretical studies have come up in the past for describing nuclei in these exotic region. Extension of traditional shell model techniques to explain the exotic feature in the structure of these nuclei such as, formation of neutron halo large r.m.s radii, soft dipole resonances etc have confirmed the necessity to modify the single particle shell model potential when dealing with nuclei far from stability. The ground state nuclear structure properties of 4Be11 have been calculated in the framework of shell model using analytically soluble mean field potential given by Ginocchio. The potential is highly versatile in nature and depends on four parameters, which define its depth, range and shape. Potential parameters, which generate highly diffuse shape, account for the small binding and halo structure of the valence neutron in 4Be11. The problem of ground state parity inversion is also addressed

    Total cross sections for the reactions 10,11,12^{10,11,12}Be+28^{28}Si and 14^{14}B+28^{28}Si

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    In this paper, the results of measurements of the total cross sections for the reactions 10,11,12^{10,11,12}Be+28^{28}Si and 14^{14}B+28^{28}Si in the beam energy range 13A13A--47A47A MeV are presented. The experimental cross sections were obtained by detection of the gamma quanta and neutrons accompanying the interaction of the isotopes of Be and B with 28^{28}Si. It was found that the cross sections for 11,12^{11,12}Be are similar, but significantly exceed those for 10^{10}Be. A significant increase in the cross sections for 12^{12}Be with decreasing energy is observed in the entire measured energy range. A theoretical explanation of the obtained experimental data is given based on the microscopic model of deformed nuclei and the numerical solution of the time-dependent Schr\"{o}dinger equation for the outer weakly bound neutrons of the projectile nuclei. The calculated total reaction cross sections are in good agreement with the experimental data

    Near-barrier Fusion and Breakup/Transfer induced by Weakly Bound and Exotic Halo Nuclei

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    The influence on the fusion process of coupling to collective degrees of freedom has been explored. The significant enhancement of the fusion cross section at sub-barrier energies was compared to predictions of one-dimensional barrier penetration models. This was understood in terms of the dynamical processes arising from strong couplings to collective inelastic excitations of the target and projectile. However, in the case of reactions where at least one of the colliding nuclei has a sufficiently low binding energy, for breakup to become an important process, conflicting model predictions and experimental results have been reported in the literature. Excitation functions for sub- and near-barrier total (complete + incomplete) fusion cross sections have been measured for the 6,7^{6,7}Li+59^{59}Co reactions. Elastic scattering as well as breakup/transfer yields have also been measured at several incident energies. Results of Continuum-Discretized Coupled-Channel ({\sc Cdcc}) calculations describe reasonably well the experimental data for both reactions at and above the barrier. A systematic study of 4,6^{4,6}He induced fusion reactions with a three-body {\sc Cdcc} method is presented. The relative importance of breakup and bound-state structure effects on total fusion (excitation functions) is particularly investigated. The four-body {\sc Cdcc} model is being currently developed.Comment: 8 pages, 3 figures; espcrc1 style; Invited Talk given at IX Int.Conf. on Nucleus-Nucleus Collisions, Rio de Janeiro Aug.2006; submitted to Nucl.Phys.

    Unveiling the intruder deformed 02+^+_2 state in 34^{34}Si

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    The 02+^+_2 state in 34^{34}Si has been populated at the {\sc Ganil/Lise3} facility through the β\beta-decay of a newly discovered 1+^+ isomer in 34^{34}Al of 26(1) ms half-life. The simultaneous detection of e+ee^+e^- pairs allowed the determination of the excitation energy E(02+^+_2)=2719(3) keV and the half-life T1/2_{1/2}=19.4(7) ns, from which an electric monopole strength of ρ2\rho^2(E0)=13.0(0.9)×103\times10^{-3} was deduced. The 21+^+_1 state is observed to decay both to the 01+^+_1 ground state and to the newly observed 02+^+_2 state (via a 607(2) keV transition) with a ratio R(21+^+_101+/21+\rightarrow0^+_1/2^+_102+\rightarrow0^+_2)=1380(717). Gathering all information, a weak mixing with the 01+^+_1 and a large deformation parameter of β\beta=0.29(4) are found for the 02+^+_2 state, in good agreement with shell model calculations using a new {\sc sdpf-u-mix} interaction allowing \textit{np-nh} excitations across the N=20 shell gap.Comment: 5 pages, 3 figures, accepted for publication in Physical Review Letter

    Direct mass measurements of 19B, 22C, 29F, 31Ne, 34Na and other light exotic nuclei

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    We report on direct time-of-flight based mass measurements of 16 light neutron-rich nuclei. These include the first determination of the masses of the Borromean drip-line nuclei 19^{19}B, 22^{22}C and 29^{29}F as well as that of 34^{34}Na. In addition, the most precise determinations to date for 23^{23}N and 31^{31}Ne are reported. Coupled with recent interaction cross-section measurements, the present results support the occurrence of a two-neutron halo in 22^{22}C, with a dominant ν2s1/22\nu2s_{1/2}^2 configuration, and a single-neutron halo in 31^{31}Ne with the valence neutron occupying predominantly the 2p3/2p_{3/2} orbital. Despite a very low two-neutron separation energy the development of a halo in 19^{19}B is hindered by the 1d5/22d_{5/2}^2 character of the valence neutrons.Comment: 5 page

    Magnetic Moment of the Fragmentation Aligned 61Fe(9/2)+ Isomer

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    We report on the g factor measurement of the isomer in 61Fe^{61}Fe (E=861keVE^{*}=861 keV). The isomer was produced and spin-aligned via a projectile-fragmentation reaction at intermediate energy, the Time Dependent Perturbed Angular Distribution (TDPAD) method being used for the measurement of the g factor. For the first time, due to significant improvements of the experimental technique, an appreciable residual alignment of the isomer has been observed, allowing a precise determination of its g factor: g=0.229(2)g=-0.229(2). Comparison of the experimental g factor with shell-model and mean field calculations confirms the 9/2+9/2^+ spin and parity assignments and suggests the onset of deformation due to the intrusion of Nilsson orbitals emerging from the νg9/2\nu g_{9/2}.Comment: 4 figures. Submitted to Phys. Rev. Let

    Neutron Transfer Dynamics and Doorway to Fusion in Time-Dependent Hartree-Fock Theory

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    We analyze the details of mass exchange in the vicinity of the Coulomb barrier for heavy-ion collisions involving neutron-rich nuclei using the time-dependent Hartree-Fock (TDHF) theory. We discuss the time-dependence of transfer and show that the potential barriers seen by individual single-particle states can be considerably different than the effective barrier for the two interacting nuclei having a single center-of-mass. For this reason we observe a substantial transfer probability even at energies below the effective barrier.Comment: 6 pages, 9 figure

    Prolate-Spherical Shape Coexistence at N=28 in 44^{44}S

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    The structure of 44^{44}S has been studied using delayed γ\gamma and electron spectroscopy at \textsc{ganil}. The decay rates of the 02+^+_2 isomeric state to the 21+^+_1 and 01+^+_1 states have been measured for the first time, leading to a reduced transition probability B(E2~:~21+^{+}_1\rightarrow02+)^{+}_2)= 8.4(26)~e2^2fm4^4 and a monopole strength ρ2\rho^2(E0~:~02+^{+}_2\rightarrow01+)^{+}_1) =~8.7(7)×\times103^{-3}. Comparisons to shell model calculations point towards prolate-spherical shape coexistence and a phenomenological two level mixing model is used to extract a weak mixing between the two configurations.Comment: 5 pages, 3 figures, accepted for publication in Physical Review Letter
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