Speaker
Dr
Tuomas Grahn
(University of Jyväskylä)
Description
In regions near magic nuclei, seniority can be regarded as a good quantum number. In the trans-Pb nuclei near the Z=82 and N=126 shell closures, relative high-j single-particle proton orbitals dominate the structure and thus levels up to I=2j−1 could, in principle, be understood within the seniority scheme. In N=122, N=124 and especially in the closed shell N=126 isotones with Z≥82, behaviour of the B(E2) values resembling the seniority scheme predictions has been observed. These nuclei lie in, or at the boundary of the region where seniority scheme could persist. However, contributions from collective excitations can not be ignored when moving away from the N=126 closed shell. To date, surprisingly little is know of the transition probabilities between the low-spin states in this region.
In the present study, B(E2;0+→2+) values have been measured in 208,210Rn and 206Po nuclei through Coulomb excitation of re-accelerated radioactive beams in inverse kinematics. The radioactive beams were produced at ISOLDE by bombarding a UCx primary target with 1.4 GeV protons. The mass separated radioactive beams were re-accelerated with the REX-ISOLDE linear accelerator to 2.8 MeV/u and delivered to the target position of the MINIBALL γ-ray spectrometer, which recorded γ-rays following Coulomb excitation. The resulting B(E2;0+→2+) values in 208,210Rn and 206Po are presented and discussed in terms of systematics and relevant nuclear models. The present study provides new insight into the interplay between collective excitations and single-particle regime near N=126.
Primary author
Dr
Tuomas Grahn
(University of Jyväskylä)
