Isoscalar dipole excitations in ${}^{16}$O

Abstract

Isoscalar (IS) monopole and dipole excitations in ${}^{16}$O were investigated by the method of shifted basis antisymmetrized molecular dynamics combined with the generator coordinate method. Significant strengths of the IS monopole and dipole transitions were obtained in the low-energy region below the giant resonances. In addition to the compressive mode, which mainly contributes to the high-energy strengths for the IS dipole giant resonance, we obtained a variety of low-energy dipole modes such as the vortical dipole mode in the $1_1^{-}$ state of the vibrating tetrahedral $4\alpha$ and the ${}^{12}$C+$\alpha$ cluster structure in the $1_2^{-}$ state. The $1_1^{-}$ state contributes to the significant low-energy strength of the IS dipole transition as 5\% of the energy-weighted sum rule, which describes well the experimental data observed by the $\alpha$ inelastic scattering.

10 pages, 6 figures

References in corpus (7)

• Exotic modes of excitation in atomic nuclei far from stability
• Alpha-particle condensation in 16O via a full four-body OCM calculation
• Evidence for tetrahedral symmetry in 16O
• Isoscalar dipole coherence at low energies and forbidden E1 strength
• Tetrahedral $4\alpha$ and ${}^{12}\text{C}+\alpha$ cluster structures in ${}^{16}$O
• Cluster and toroidal aspects of isoscalar dipole excitations in ${}^{12}$C
• Low-energy dipole excitation modes in ${}^{10}$Be

Cited by in corpus (3)

• A variety of clustering in ${}^{18}$O
• Monopole and dipole transitions of the cluster states of 18O
• alpha+28Si and 16O+16O molecular states, and their isoscalar monopole strengths