Low-energy dipole excitation modes in $^{10}$Be

Abstract

Low-energy dipole excitations in 10 Be were investigated based on the generator coordinate method with α + 6 He and α + α + 2n cluster models. We obtained three 1 − states in E x < 15 MeV, which show different characters in the E1, compressive dipole, and toroidal dipole transition strengths. We found the strong toroidal dipole transition in the 1 − 1 state, remarkable E1 strength in the 1 − 2 state, and the strong E1 and compressive dipole strength in the 1 − 3 state. The 1 − 1 is described by the α + 6 He cluster structure, where as the 1 − 2 and 1 − 3 states are understood by three-body excitations of the α + α + 2n clustering.

Isoscalar monopole and dipole transitions inMg24,Mg26, andSi

“…The extracted IS1 and IS0 strength distributions were compared to the theoretical calculations performed within the Skyrme Quasiparticle Random-Phase-Approximation (QRPA) [48][49][50][51] and Antisymmetrized Molecular Dynamics + Generator Coordinate Method (AMD+GCM) [10][11][12][13][14] approaches. The correspondence, at least tentative, between some calculated and observed states was established.…”

“…The low-energy isoscalar monopole (IS0) and dipole (IS1) states in light nuclei can serve as fingerprints of clustering [5,6] one of the basic features of light nuclei. IS1 states can also deliver important information on some mean-field features, such as vorticity [7][8][9][10][11][12][13][14].…”

“…In addition to this clustering behaviour, mean-field structures may also exist. Individual low-lying vortical IS1 states were predicted within the Quasiparticle Random-Phase-Approximation (QRPA) [7][8][9] and the Antisymmetrized Molecular Dynamics + Generator Coordinate Method (AMD+GCM) [10][11][12][13][14]. These states should exist in 10 Be [10,11], 12 C [12], 16 O [13], 20 Ne [8], and 24 Mg [7][8][9]14].…”

“…The theoretical analysis is performed within the QRPA model for axially deformed nuclei [48][49][50][51][52] and the AMD+GCM model [10][11][12][13][14] which can take into account both axial and triaxial quadrupole deformations and describe the evolution of the nuclear shape with excitation energy. Moreover, AMD+GCM includes the ability to describe the interplay between mean-field and cluster degrees of freedom.…”

Low-energy dipole excitations in $^{20}$O with antisymmetrized molecular dynamics

“…For example, the neutron skin mode (Pigmy mode) [15,16] was considered for E1 strengths [1][2][3][4]. To understand isoscalar LED strengths, toroidal (also called vortical or torus) were suggested [1,[17][18][19][20][21][22][23][24][25], and cluster modes were investigated [26][27][28][29][30][31][32]. However, the observed LED strengths were not fully described, and their origins are not clarified yet.…”