Low-lying isoscalar dipole excitations in 208Pb

Decowski, P.; Morsch, H. P.; Benenson, W.

doi:10.1016/0370-2693(81)90661-4

Cited by 18 publications

(7 citation statements)

References 16 publications

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“…A central issue is possible appearance of new excitation modes decoupled from collective vibration modes corresponding the giant resonances (GR). In experiments with α inelastic scattering extensively performed for study of isoscalar (IS) monopole and dipole excitations, significant low-energy strengths with the fraction of several percentages of the energy weighted sum rule have been observed in various stable nuclei such as 16 O, 40 Ca, and 208 Pb [6][7][8]. The questions to be answered are what is the origin of these IS low-energy dipole (LED) strengths and how the dipole modes come down to the energy much lower than the IS giant dipole resonances (GDR).…”

Section: Introductionmentioning

confidence: 99%

Isoscalar dipole excitations inO16

Kanada-En’yo

Shikata

2019

Phys. Rev. C

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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 4α and the 12 C+α 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 α inelastic scattering.

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Section: Introductionmentioning

confidence: 99%

Isoscalar dipole excitations inO16

Kanada-En’yo

Shikata

2019

Phys. Rev. C

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“…The IS giant dipole resonances (GDR), which correspond to the collective compressive dipole mode, have been observed for stable nuclei in the energy region higher than that of the IVGDR for the proton-neutron opposite oscillation mode. Below the ISGDR, significant LE-ISD strengths have been known in stable nuclei [7][8][9]. In the ISD strengths of 16 O and 40 Ca, 4 − 5% of the energy weighted sum rule have been observed in the E ≤ 10 MeV region.…”

Section: Introductionmentioning

confidence: 99%

Cluster and toroidal aspects of isoscalar dipole excitations in C12

2018

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We investigated cluster and toroidal aspects of isoscalar dipole excitations in 12 C based on the shifted basis antisymmetrized molecular dynamics combined with the generator coordinate method, which can describes 1p-1h excitations and 3α dynamics. In the E = 10 − 15 MeV region, we found two low-energy dipole modes separating from the giant dipole resonance. One is the developed 3α-cluster state and the other is the toroidal dipole mode. The cluster state is characterized by the large amplitude cluster motion beyond the 1p-1h model space, whereas the toroidal dipole mode is predominantly described by 1p-1h excitations on the ground state. The low-energy dipole states are remarkably excited by the toroidal dipole operator, which can measure the nuclear vorticity. For compressive dipole transition strengths, a major part is distributed in the 30 − 50 MeV region for the giant dipole resonance, and 5% of the total energy weighted sum exist in the E < 20 MeV region.

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“…(In some works, the word "PDR" is used to call this specific mode.) Also in IS dipole (ISD) excitations, low-energy strengths known in such nuclei as 16 O, 40 Ca, and 208 Pb [12,15,16] have been discussed in relation to an exotic dipole mode, i.e., the toroidal dipole (TD) mode [1,14,[17][18][19][20][21][22][23] The TD mode carries vorticity and its character is much different from the compressive dipole (CD) mode, which is the normal mode for the ISGDR. In this decade, IS and IV properties of low-energy dipole excitations have been intensively studied to clarify essential nature of lowenergy dipole modes [1,3,4].…”

Section: Introductionmentioning

confidence: 99%

Toroidal, compressive, and E1 properties of low-energy dipole modes in Be10

Kanada-En’yo

Shikata

2017

Phys. Rev. C

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We studied dipole excitations in 10 Be based on an extended version of the antisymmetrized molecular dynamics, which can describe 1p-1h excitations and large amplitude cluster modes. Toroidal and compressive dipole operators are found to be good proves to separate the low-energy and highenergy parts of the isoscalar dipole excitations, respectively. Two low-energy 1 − states, the toroidal dominant 1 − 1 state at E ∼ 8 MeV and the E1 dominant 1 − 2 state at E ∼ 16 MeV, were obtained. By analysis of transition current densities, the 1 − 1 states is understood as a toroidal dipole mode with exotic toroidal neutron flow caused by rotation of a deformed 6 He cluster, whereas the 1 − 2 state is regarded as a neutron-skin oscillation mode, which are characterized by surface neutron flow with inner isoscalar flow caused by the surface neutron oscillation against the 2α core.

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Low-lying isoscalar dipole excitations in 208Pb

Cited by 18 publications

References 16 publications

Isoscalar dipole excitations inO16

Isoscalar dipole excitations inO16

Cluster and toroidal aspects of isoscalar dipole excitations in C12

Toroidal, compressive, and E1 properties of low-energy dipole modes in Be10

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