Single-particle states and parity doublets in odd- Z Ac221 and Pa225 from

Abstract

Low-lying states in the odd-Z isotopes 221 89 Ac 132 and 225 91 Pa 134 have been studied using α-particle and αγcoincidence spectroscopy in the 225 Pa → 221 Ac → 217 Fr decay chain. Ground-state spin and parity assignments of I π = 5/2 − are proposed for both 221 Ac and 225 Pa, with the odd proton occupying the = 5/2 orbital of the quadrupole-octupole deformed shell model in both nuclei. In 221 Ac, excited states in the bands based on the = 5/2 and = 3/2 orbitals have been identified, including proposed parity-doublet states. The results suggest that reflection-asymmetric deformation of the ground state persists in the odd-A members of the isotope chains down to N = 132 for Ac and N = 134 for Pa, before reaching the transitional region at N = 130.

Level structure of Ac221 and Fr217 from decay spectroscopy, and reflection asymmetry in Rey-Herme1, Raggio2, Vandebrouck3 et al. 2023Phys. Rev. CSelf Cite2000View full textAdd to dashboardCite

“…The α decay of 225 Pa has previously been reported in several references [24][25][26][27][28][29]. The most extensive study [24], published recently, reports seven α-decay branches with energies, intensities and hindrance factors given in Table I, as well as four γ -ray transitions observed in coincidence for the first time.…”

“…The α decay of 225 Pa has previously been reported in several references [24][25][26][27][28][29]. The most extensive study [24], published recently, reports seven α-decay branches with energies, intensities and hindrance factors given in Table I, as well as four γ -ray transitions observed in coincidence for the first time. In this recent work, the authors assign a I π = 5/2 − to the ground state for both 221 Ac and 225 Pa. For comparison the previous work of Huyse and collaborators had clean αenergy spectra showing three α-decay branches with energies and branching ratios [7261 (5) keV, 53(2)%], [7235(5) keV, 30(2)%], and [7170(5) keV, 17(1)%] (see Fig.…”

“…As mentioned above, there is a disagreement on the spin assignment of the ground state of 221 Ac between the inbeam [30] and α-decay [24] experiments. The α decay of 221 Ac has been studied several times in the past [24][25][26][27]29], with the most recent one [24] reporting three α-decay branches (see Table I) consistent with the previously measured ones, as well as three γ transitions measured in coincidence for the first time. In Ref.…”

Nuclear Physics Opportunities at European Small-Scale Facilities

“…It has led to the shortest directly measured half-life of 450 +170 −100 ns for a ground-state proton emitter. Low-lying states in the odd-Z isotopes 221 Ac and 225 Pa have been studied using α-particle and αγ -coincidence spectroscopy in the 225 Pa → 221 Ac → 217 Fr decay chain [106]. The target was located at the center of the SAGE spectrometer.…”

“…Especially in the cases where low cross-sections are involved, a 4π detector (such as the one included in RUBION) allows the total cross-section of a reaction to be determined in comparatively short time periods. One of the fields of the study at RUBION [108] is (α,γ) reactions that are relevant to the p-process, in particular, 102 Pd(α,γ) 106 Cd and 73 Ge(α,γ) 77 Se. The goal of this research is to provide experimental data in unexplored energy regions and at beam energies where the available experimental data are insufficient to firmly constrain the theoretical model calculations.…”