Particle spectra and particle-vibration coupling in the Pb region

New μs isomers in the neutron-rich 210 Hg nucleus

“…In more neutron-rich nuclei further reduction of the excitation energy is expected [21]. For example, in 214 Po, which has the same neutron number of 210 Hg and two protons above Z=82 shell closure ( 210 Hg has two protons below), the energy of the 3 − state is at around 1.3 MeV [22], the value which is predicted also in 210 Hg by particle-vibration coupling models [21], as shown in Fig. 3.…”

“…3), but cannot reliably predict the location of a 3 − state. This is because the present shell-model calculations do not allow core excitations and it is known that the 3 − state in the lead region is very fragmented [21], involving many particlehole excitations across the 208 Pb core. As a consequence, shell model calculations do not predict any excited state below 1.1 MeV, apart from the first excited 2 + state.…”

“…As a consequence, shell model calculations do not predict any excited state below 1.1 MeV, apart from the first excited 2 + state. By looking at the systematics of 3 − excitations in this region, one observes that the 3 − level is at 2.6 MeV in 208 Pb and drops to 1.9 MeV in 210 Pb due to mixing between the collective 208 Pb octupole phonon and the 3 − originating from the octupole coupling of the ∆J = ∆ℓ = 3 neutron shells g 9/2 − j 15/2 [21]. In more neutron-rich nuclei further reduction of the excitation energy is expected [21].…”

“…By looking at the systematics of 3 − excitations in this region, one observes that the 3 − level is at 2.6 MeV in 208 Pb and drops to 1.9 MeV in 210 Pb due to mixing between the collective 208 Pb octupole phonon and the 3 − originating from the octupole coupling of the ∆J = ∆ℓ = 3 neutron shells g 9/2 − j 15/2 [21]. In more neutron-rich nuclei further reduction of the excitation energy is expected [21]. For example, in 214 Po, which has the same neutron number of 210 Hg and two protons above Z=82 shell closure ( 210 Hg has two protons below), the energy of the 3 − state is at around 1.3 MeV [22], the value which is predicted also in 210 Hg by particle-vibration coupling models [21], as shown in Fig.…”

New Isomers in the Full Seniority Scheme of Neutron-Rich Lead Isotopes: The Role of Effective Three-Body Forces

“…Therefore, the large-scale shell-model calculations not only cannot reproduce the hindrance of the BðE2Þ values in 212 Pb but also introduce an asymmetry around midshell not present in the experimental data. One objection to our calculations could arise from the value of the single particle energy of the j 15=2 orbital taken from the spectrum of 209 Pb, due the presence of a strong mixture of j 15=2 and g 9=2 3 À [22]. If half of the spectroscopic strength is assumed to be at about 3.5 MeV [23], then the singleparticle energy has to be shifted by 1 MeV: the disagreement with the BðE2Þ rates decreases, though it does not vanish, as shown in Fig.…”