Shell evolution of stable N = 50-56 Zr and Mo nuclei with respect to low-lying octupole excitations

For the N = 50-56 zirconium (Z = 40) and molybdenum (Z = 42) isotopes, the evolution of subshells is evaluated by extracting the effective single-particle energies from available particle-transfer data. The extracted systematic evolution of neutron subshells and the systematics of the excitation energy of the octupole phonons provide evidence for type-II shape coexistence in the Zr isotopes. Employing a simplistic approach, the relative effective single-particle energies are used to estimate whether the formation of low-lying octupole-isovector excitations is possible at the proposed energies. The results raise doubts about this assignment

Quadrupole collectivity in neutron-rich Cd isotopes

4 pags., 2 figs. -- INPC 2013 – International Nuclear Physics ConferenceThe investigation of the excitation energies of the 21+ –states in the neutron-rich Cd isotopes shows an irregular behaviour when approaching the neutron shell-closure at N = 82. The energy of the 21+–state in 128Cd is lower than the one in 126Cd. The transition strength B(E2, 0gs+ → 21+) in the even isotopes 122−128Cd was measured in Coulomb excitation experiments with the high-purity germanium detector array MINIBALL at REXISOLDE (CERN). The values for 122,124Cd coincide with beyond-mean-field calculations with a resultant prolate deformation, whereas 126,128Cd are better described by shell-model calculations.This project is supported by BMBF (No. 06 DA 9036I, No. 05 P12 RDCIA, No. 05 P12 RDCIB and No. 05 P12 PKFNE), HIC for FAIR, EU through EURONS (No. 506065) and ENSAR (No. 262010) and the MINIBALL and REX-ISOLDE collaborations

Identification of low-energy isovector octupole states in ¹⁴⁴Nd

Recently, first candidates for low-lying isovector states in the octupole sector were suggested. The unambiguous identification of those states will contribute to the decomposition of the octupole-octupole residual interaction in an isoscalar and isovector part. This will help us understand the octupole degree of freedom. In ¹⁴⁴Nd the 3⁻ state at 2778 keV is a good candidate for such a “mixed-symmetry’' octupole state. In order to clarify the nature of this state, a ¹⁴³Nd(n, γ)-experiment was conducted with the EXILL-setup. Following neutron capture the 3⁻ states are populated and EXILL provides the opportunity to determine the multipole-mixing ratios of the 3i⁻→3₁⁻ transitions. For the transition from the “mixed-symmetry” octupole state to the symmetric 3₁⁻ state we expect a strong M1 component

First EXL experiment with radioactive beam: Proton scattering on 56^{56}Ni

EXL (EXotic nuclei studied in Light-ion induced reactions at the NESR storage ring) is a project within NUSTAR at FAIR. It aims at investigations of light-ion induced direct reactions in inverse kinematics with radioactive ions cooled and stored in the future NESR (New Experimental Storage Ring). The existing ESR (Experimental Storage Ring) at GSI, together with its internal gas-jet target, provides a unique opportunity to perform such kind of experiments on a smaller scale at the present time. We have developed a UHV-compatible (Ultra High Vacuum) detector setup mainly based on DSSDs (Double-sided Silicon-Strip Detector) for the target-like recoils [4]. With this setup we were able to successfully investigate reactions with a stored radioactive beam for the first time ever. As a part of the first EXL campaign we investigated the reaction 56Ni(p,p)56Ni in inverse kinematics in order to measure the differential cross section for elastic proton scattering and deduce the nuclear-matter distribution and radius of 56Ni. In the following, the experimental setup is introduced in more detail, and the current status of the ongoing analysis is discussed

Nuclear reactions in the storage ring ESR with EXL

The EXL project aims to study nuclear structure by direct reactions in inverse kinematics at the storage rings of the future FAIR facility. In this contribution, we present the status of the project: the technical implementation at the ESR at GSI and preliminary results of the EXL campaign in 2012, the first using also a radioactive beam

Coulomb excitation of re-accelerated 208Rn and 206Po beams

Volume: 63Peer reviewe

Quadrupole collectivity in neutron-rich Cd isotopes

The investigation of the excitation energies of the 2(1)(+)-states in the neutron-rich Cd isotopes shows an irregular behaviour when approaching the neutron shell-closure at N = 82. The energy of the 2(1)(+)-state in Cd-128 is lower than the one in Cd-126. The transition strength B(E2, 0(gs)(+) -> 2(1)(+)) in the even isotopes Cd122-128 was measured in Coulomb excitation experiments with the high-purity germanium detector array MINIBALL at REX-ISOLDE (CERN). The values for Cd-122,Cd-124 coincide with beyond-mean-field calculations with a resultant prolate deformation, whereas Cd-126,Cd-128 are better described by shell-model calculations