Precision mass measurements of Cd125–127 isotopes and isomers approaching the N=82 closed shell

Abstract

We present the results of precision mass measurements of neutron-rich cadmium isotopes. These nuclei approach the N = 82 closed neutron shell and are important to nuclear structure as they lie near doubly-magic 132 Sn on the chart of nuclides. Of particular note is the clear identification of the ground state mass in 127 Cd along with the isomeric state. We show that the ground state identified in a previous mass measurement which dominates the mass value in the Atomic Mass Evaluation is an isomeric state. In addition to 127/m Cd, we present other cadmium masses measured ( 125/m Cd and 126 Cd) in a recent TITAN experiment at TRIUMF. Finally, we compare our measurements to new ab initio shell-model calculations and comment on the state of the field in the N = 82 region.

First Glimpse of the N=82 Shell Closure below Z=50 from Masses of Neutron-Rich Cadmium Isotopes and Isomers

“…This means that without data for nuclides with Z < 50 and N ≈ 82, any predictions for the N = 82 shell gap are rather uncertain. While decayspectroscopy [16][17][18], laser-spectroscopy [19] and massspectrometry [20,21] studies have been performed for the neutron-rich cadmium isotopes, the energies of the low-lying isomers in 129 Cd and the N = 82 two-neutron shell gap remain unknown.The A ≈ 130 r-process abundance peak has long been considered an indication of a persistent N = 82 shell gap in various models. However, recent studies of r-process nucleosynthesis have underlined the importance of fission recycling in certain scenarios, in which the A = 130 abundance peak is primarily determined by the fissionfragment distribution of r-process actinides [22,23].In this work, we present the first direct determination of the N = 82 shell gap for Z < 50 with mass measurements of exotic cadmium isotopes and isomers between 124 Cd and 132 Cd.…”

“…This means that without data for nuclides with Z < 50 and N ≈ 82, any predictions for the N = 82 shell gap are rather uncertain. While decayspectroscopy [16][17][18], laser-spectroscopy [19] and massspectrometry [20,21] studies have been performed for the neutron-rich cadmium isotopes, the energies of the low-lying isomers in 129 Cd and the N = 82 two-neutron shell gap remain unknown.…”

β decay of Cd127 and excited states in In127Lorenz1, Sarmiento2, Rudolph3 et al. 2019Phys. Rev. C110110View full textAdd to dashboardCite

“…A recent mass measurement yielded a consistent excitation energy of 390 (18) keV [17]. In addition to the 1/2 − isomer, another β-decaying isomer at 1697 (49) keV with a tentative spin-parity assignment of I π = 21/2 − and T 1/2 = 1.04 (10) s has been identified [16,17]. Evidence for a short-lived, T 1/2 = 9(2) μs, high-spin isomer feeding this 21/2 − isomer has been found as well, with a tentative 29/2 + spin-parity assignment [18,19].…”

“…II), the individual β-decay branching ratios for these two states are calculated in Table II. In the last column of Table II the corresponding log f t values are listed, calculated using the LOGFT code [42] with the half-lives discussed earlier, a Q value of Q β = 8149(24) keV [43], and an excitation energy of 283.3(56) keV [10] for the 11/2 − isomer.…”

“…The reported decay scheme of 127 In suggested only one β-decaying state in 127 Cd with a half-life of T 1/2 = 0.43(3) s. Later studies identified two longlived states with spin-parity assignments I π = 11/2 − and I π = 3/2 + , respectively [9]. Recently, the excitation energy of the isomer in 127 Cd was measured to be 283.3 (56) keV [10].…”