Origin of Low-Lying EnhancedE1Strength in Rare-Earth Nuclei

Abstract

The experimental E1 strength distribution below 4 MeV in rare-earth nuclei suggests a local breaking of isospin symmetry. In addition to the octupole states, additional J π = 1 − states with enhanced E1 strength have been observed in rare-earth nuclei by means of (γ,γ') experiments. By reproducing the experimental results, the spdf interacting boson model calculations provide further evidence for the formation of an α cluster in medium-mass nuclei and might provide a new understanding of the origin of low-lying E1 strength.

Decay of quadrupole-octupole1−states inCa40andCe140Derya1, Tsoneva2, Aumann3 et al. 2016Phys. Rev. CSelf Cite12120View full textAdd to dashboardCite

“…Another model which has been intensively applied in studies of multi-phonon states [43,44] is the interacting boson model (IBM) [45]. Recently, the spdf IBM has been applied in systematical studies of lowlying J =1 states in the Nd isotopes and other rare-earth nuclei [31].…”

“…These include the low-energy tail of the IVGDR, PDR [18,19,27,28], multi-phonon excitations [19,29], toroidal modes [23] and α-cluster vibrations [30,31]. Furthermore, in recent studies it has been pointed out that the interaction between quasiparticles and phonons is important for a correct theoretical description of the low-lying E1 strength because it can influence its fragmentation and mixing with the core polarization and the IVGDR [18,19,29,[32][33][34][35].…”

Isoscalar dipole transition as a probe for asymmetric clustering

“…The α clustering in the actinides [49][50][51] were also investigated in the same literature. Recently, the α clustering in 212 Po [52][53][54] and the rare-earth nuclei [55] were also discussed based on their enhanced low-lying E1 strengths.…”

α clustering and its connection to the E1 response of heavy nuclei

“…The low-lying E1 response of A < 100 nuclei As pointed out in the introduction, it is very interesting to test if the conclusions of the rareearth region [3] could be extended to other mass regions. For this test, the three nuclei 48 Ti, 74 Ge, and 94 Mo have been chosen.…”

“…In this contribution, the α-cluster dipole mode will be discussed, which was investigated in the framework of the spdf interacting boson model (IBM). First results for the low-lying E1 strength in rare-earth nuclei have already been presented and a close connection of the origin of E1 strength with the collective p boson was established [3]. The p boson is geometrically identified with a two-body cluster configuration, see, e.g., Refs.…”