320 research outputs found
Pairing and deformation effects in nuclear excitation spectra
We investigate effects of pairing and of quadrupole deformation on two sorts
of nuclear excitations,-vibrational states and dipole
resonances (isovector dipole, pygmy, compression, toroidal). The analysis is
performed within the quasiparticle random-phase approximation (QRPA) based on
the Skyrme energy functional using the Skyrme parametrization SLy6. Particular
attention is paid to i) the role of the particle-particle (pp) channel in the
residual interaction of QRPA, ii) comparison of volume pairing (VP) and surface
pairing (SP), iii) peculiarities of deformation splitting in the various
resonances. We find that the impact of the pp-channel on the considered
excitations is negligible. This conclusion applies also to any other excitation
except for the states. Furthermore, the difference between VP and
SP is found small (with exception of peak height in the toroidal mode). In the
low-energy isovector dipole (pygmy) and isoscalar toroidal modes, the branch
is shown to dominate over one in the range of
excitation energy 8--10 MeV. The effect becomes impressive for the
toroidal resonance whose low-energy part is concentrated in a high peak of
almost pure nature. This peculiarity may be used as a fingerprint
of the toroidal mode in future experiments. The interplay between pygmy,
toroidal and compression resonances is discussed, the interpretation of the
observed isoscalar giant dipole resonance is partly revised.Comment: 12 pages, 12 figure
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