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 Jπ and T1/2 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 Jπ 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 β− 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).