Abstract
The isoscalar monopole (ISM) and dipole (ISD) excitations in are investigated theoretically with the shifted antisymmetrized molecular dynamics (AMD) plus -cluster generator coordinate method (GCM). The small-amplitude vibration modes are described by coherent one-particle one-hole excitations expressed by a small shift of single-nucleon Gaussian wave functions within the AMD framework, whereas the large-amplitude cluster modes are incorporated by superposing -cluster wave functions in the GCM. The coupling of the excitations in the intrinsic frame with the rotation and parity transformation is taken into account microscopically by the angular-momentum and parity projections. The present a calculation that describes the ISM and ISD excitations over a wide energy region covering cluster modes in the low-energy region and the giant resonances in the high-energy region, although the quantitative description of the high-energy part is not satisfactory. The low-energy ISM and ISD strengths of the cluster modes are enhanced by the distance motion between clusters, and they split into a couple of states because of the angular motion of clusters. The low-energy ISM strengths exhaust 26% of the energy-weighted sum rule, which is consistent with the experimental data for the (; 7.65 MeV) and (; 10.3 MeV) measured by , and () scatterings. In the calculated low-energy ISD strengths, two states (the and states) with the significant strengths are obtained over MeV. The results indicate that the ISD excitations can be a good probe to experimentally search for new cluster states such as the obtained in the present calculation.
- Received 11 December 2015
DOI:https://doi.org/10.1103/PhysRevC.93.054307
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