Nuclear Structure and Decay Data for A = 222 Isobars

Abstract

Evaluated data are presented for 11 known $A=222$ nuclides (Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, and Np), and relevant J^π and T_1/2 data for $A=226$ nuclei decaying by α-decay to $A=222$ nuclei. For ²²²Bi, only the isotopic identification is established with no measurement of its half-life. For ²²²Po, ²²²At, ²²²Fr, ²²²U, and ²²²Np, data are available only for the ground states, with static magnetic dipole and electric quadrupole moments, and charge radius measurements for the ²²²Fr ground state. For ²²²Ac and ²²²Pa, two low-lying levels are known from ²²⁶Pa α decay, and ²²⁶Np decay, respectively, but with no information about J^π assignments and γ decays of these levels. For ²²²Pa, a long-lived isomeric state is known, decaying dominantly by α decay. ²²²Rn, ²²²Ra, and ²²²Th have been investigated in detail, the low-spin states by α decay and the high-spin studies of ground-state and octupole bands by in-beam γ-ray studies for all the three nuclei, as well as by Coulomb excitation for ²²²Rn and ²²²Ra. Low-spin levels in ²²²Ra have been investigated also through the ${\beta }^{-}$ decay of ²²²Fr. Half-lives of the excited states are known for 7 levels in ²²²Rn, 12 levels in ²²²Ra, and 3 levels in ²²²Th. Octupole deformations, with the presence of alternating-parity bands up to (16⁺) and (${21}^{-}$) in ²²²Rn, (20⁺) and (${19}^{-}$) in ²²²Ra, and (26⁺) and (${25}^{-}$) in ²²²Th, and with interband E1 transitions, have been established in these three nuclei. The present evaluation supersedes the previous $A=222$ ENSDF evaluations: (2011Si24), (1996El01), (1987El06) and (1977To14).