Speaker
Description
The nuclear shell model, combined with pairing correlations, offers a straightforward explanation of the low-energy spectra of semi-magic nuclei. In a single high-$j$ orbital with more than two particles, low-lying $J>0$ states arise from recoupling of unpaired nucleons and group into multiplets labeled by seniority $\nu$—the number of unpaired particles. The generalized seniority scheme is essentially a truncated shell-model description~\cite{Talmi1971}. To study how well the seniority picture holds near the $N=126$ shell closure, we carried out a safe Coulomb-excitation experiment on $^{214}\mathrm{Ra}$. A post-accelerated $^{214}\mathrm{Ra}$ beam was directed onto a $^{120}\mathrm{Sn}$ target at HIE-ISOLDE, and the resulting $\gamma$ rays were measured with the Miniball detector~\cite{Warr2013}. Our main goal is to extract $B(E2; 2_1^+ \!\rightarrow\! 0_1^+)$ transition strength and compare it with expectations from the nuclear shell model and with trends seen in neighboring $N=126$ isotones. With data taking completed and analysis in progress, we present the current status along with preliminary $B(E2)$ values. Once finished, these results will test whether the low-lying states of $^{214}\mathrm{Ra}$ are dominated by a simple $\pi(1h_{9/2})^{2}$ configuration, and they will provide useful constraints for model parameters used in this region.
References
[1]I.Talmi, Nucl. Phys. A 172, 1 (1971).
[2]N.Warr et al.,Eur. Phys. J. A 49, 40 (2013).
