Lifetimes of the $2_1^{+}$ and $4_1^{+}$ states of the neutron-rich nuclide ${}^{200}$Pt

The lifetimes of the $2_1^{+}$ and $4_1^{+}$ states of ${}^{200}$Pt were measured applying the recoil-distance Doppler-shift method. Excited states were populated in the ${}^{198}$Pt(${}^{18}$O, ${}^{16}$O)${}^{200}$Pt two-neutron transfer reaction at the $9\text{MV}$ tandem accelerator at the IFIN-HH in Măgurele, Romania. The resulting $B(E2)$ values of the $2_1^{+}\to 0_1^{+}$ and $4_1^{+}\to 2_1^{+}$ transitions as well as the $B_{4\mathrm{/}2}$ ratio of $2.08(32)$ indicate the nuclear structure evolving towards sphericity when approaching the neutron shell closure at $N=126$. The $B(E2;2_1^{+}\to 0_1^{+})$ values of Pt and Hg are compared to values of Te, Xe and Ba as both regions of the nuclear chart show similar structural effects.