Low-frequency quadrupole vibrational modes in deformed
36,38,40Mg close to the neutron drip line are studied by means of the quasiparticle-random-phase approximation based on the coordinate-space ...Hartree–Fock–Bogoliubov formalism. Strongly collective
K
π
=
0
+
and
2
+
excitation modes carrying 10–20 Weisskopf units in the intrinsic isoscalar quadrupole transition strengths are obtained at about 3 MeV. There are two reasons for the enhancement of the transition strengths. First, the quasiparticle wave functions generating these modes possess spatially very extended structure. The asymptotic selection rules characterizing the
β and
γ vibrations in stable deformed nuclei are thus strongly violated. Second, the dynamic pairing effects act strongly to enhance the collectivity of these modes. It is suggested that the lowest
K
π
=
0
+
collective mode is a particularly sensitive indicator of the nature of pairing correlations in deformed nuclei close to the neutron drip line.
The Hartree-Fock-Bogoliubov equations for deformed weakly bound nuclei are solved using a basis of Poschl-Teller-Ginocchio and Bessel/Coulomb wave functions, which possess proper asymptotic behavior. ...Results compare well with standard Hartree-Fock- Bogoliubov calculations using box boundary condition or transformed harmonic oscillator basis.
Investigations of exotic cluster-like phenomena in the framework of the Skyrme-Hartree-Fock approach are reported. The occurrence of highly excited isomeric states is discussed in connection with the ...question of their stability in static and time-dependent Hartree Fock (TDHF) calculations. We find rotational stabilization of a 4α chain structure in 16O occurring for a limited range of angular momenta. A toroidal configuration of 40Ca was also stabilized by rotation and provides a very interesting example of rotation about a symmetry axis with a strictly quantized total angular momentum. Finally we look at the formation of nuclear pasta phases in a time-dependent approach and their classification.
On the basis of the cranked Skyrme–Hartree–Fock calculations in the three-dimensional coordinate-mesh representation, we suggest that, in addition to the well-known candidate
32S, the neutron-rich ...nucleus
36S and the drip-line nuclei,
48S and
50S, are also good candidates for finding superdeformed rotational bands in sulfur isotopes. Calculated density distributions for the superdeformed states in
48S and
50S exhibit superdeformed neutron skins.
Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, ...46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.
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