0000000000636615
AUTHOR
K. F. Mulholland
Identification of the Jπ = 1− state in 218Ra populated via α decay of 222Th
The α decay of 222Th populating the low-lying J π = 3− state, and also a proposed 1− state, in 218Ra 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. peerReviewed
Direct observation of the Ba 114 → Xe 110 → Te 106 → Sn 102 triple α -decay chain using position and time correlations
The triple α-decay chain 114Ba → 110Xe → 106Te → 102Sn has been directly observed for the first time, following the 58Ni(58Ni ,2n) reaction. Implantation of 114Ba nuclei into a double-sided silicon-strip detector has allowed their α decays to be correlated in position and time with the α decays of the daughter (110Xe) and granddaughter (106Te) nuclei. In total, 17 events have been assigned to the 114Ba → 110Xe → 106Te → 102Sn triple α-decay chain. The energy of the 114Ba α decay has been measured to be Eα = 3480(20) keV, which is 70 keV higher than the previously measured value, and the half-life of 114Ba has been measured with improved accuracy, to be 380+190 −110 ms. A revised Q12C value …
Excited states in 217Ra populated in the α decay of 221Th
Fine structure in the α decay of 22190Th, populating excited states in 21788Ra, was studied using αγ-coincidence spectroscopy. Two α-decay branches from 221Th have been newly observed, with Eα(keV)[bα(%)]=7951(8)[0.14(3)] and 8247(3)[1.51(12)], together with three previously known branches. Also, two new states in 217Ra were identified at E = 177 and 227 keV. The ground-state configurations of the odd-A, N = 131 transitional isotones above 208Pb are interpreted from their α-decay fine structure systematics and considered in terms of predictions using spherical shell and reflection-asymmetric models. peerReviewed
α-decay spectroscopy of the N = 130 isotones 218Ra and 220Th: Mitigation of α-particle energy summing with implanted nuclei
An analysis technique has been developed in order to mitigate energy summing due to sequential short-lived α decays from nuclei implanted into a silicon detector. Using this technique, α-decay spectroscopy of the N=130 isotones 218Ra (Z=88) and 220Th (Z=90) has been performed. The energies of the α particles emitted in the 218Ra→214Rn and 220Th→216Ra ground-state-to-ground-state decays have been measured to be 8381(4) keV and 8818(13) keV, respectively. The half-lives of the ground states of 218Ra and 220Th have been measured to be 25.99(10) μs and 10.4(4) μs, respectively. The half-lives of the ground states of the α-decay daughters, 214Rn and 216Ra, have been measured to be 259(3) ns and …
Delayed or absent π(h11/2)2 alignment in 111Xe
Excited states have been identified in the very neutron-deficient N = Z + 3 nucleus 111Xe for the first time, using the 58Ni(58Ni, αn) heavy-ion fusion-evaporation reaction. γ -ray transitions have been unambiguously assigned to 111Xe by correlation with the characteristic 111Xe → 107Te → 103Sn α-decay chain using the method of recoil-decay tagging. Inspection of γ γ -coincidence data has shown that five of the transitions form a rotational-like sequence. Excitation-energy systematics suggest that the sequence could be the favored signature partner of a band built on an h11/2 neutron. Aligned angular momenta of states in the band have been compared to analogous bands in neighboring xenon is…