The α decay of 222 Th populating the low-lying J π = 3 − state, and also a proposed 1 − state, in 218 Ra has been observed. The observations suggest an excitation energy of 853 keV for the 1 − state, which is 60 keV above the 3 − state. The hindrance factors of these α decays give a possible boundary to the region of ground-state octupole deformation in the light-actinide nuclei. The relative positions of the J π = 1 − and 3 − states suggest they are produced by an octupole-vibrational mechanism, as opposed to α clustering or rotations of a reflection-asymmetric octupole-deformed shape.

The lifetime of the 2 + → 0 + g.s. transition in the neutron-deficicient nucleus 112 Te has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift technique. The deduced value for the reduced transition probability is B(E2 :0 + g.s. → 2 + ) = 0.46 ± 0.04 e 2 b 2 , indicating that there is no unexpected enhancement of the B(E2 :0 + g.s. → 2 + ) values in Te isotopes below the midshell. The result is compared to and discussed in the framework of large-scale shell-model calculations.

Lifetimes of the first excited 2^{+} and 4^{+} states in the extremely neutron-deficient nuclide ^{172}Pt have been measured for the first time using the recoil-distance Doppler shift and recoil-decay tagging techniques. An unusually low value of the ratio B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+})=0.55(19) was found, similar to a handful of other such anomalous cases observed in the entire Segré chart. The observation adds to a cluster of a few extremely neutron-deficient nuclides of the heavy transition metals with neutron numbers N≈90-94 featuring the effect. No theoretical model calculations reported to date have been able to explain the anomalously low B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+}) ratios observed in these cases. Such low values cannot, e.g., be explained within the framework of the geometrical collective model or by algebraic approaches within the interacting boson model framework. It is proposed that the group of B(E2:4_{1}^{+}→2_{1}^{+})/B(E2:2_{1}^{+}→0_{gs}^{+}) ratios in the extremely neutron-deficient even-even W, Os, and Pt nuclei around neutron numbers N≈90-94 reveal a quantum phase transition from a seniority-conserving structure to a collective regime as a function of neutron number. Although a system governed by seniority symmetry is the only theoretical framework for which such an effect may naturally occur, the phenomenon is highly unexpected for these nuclei that are not situated near closed shells.