Abstract
We probe the N=82 nuclear shell closure by mass measurements of neutron-rich cadmium isotopes with the ISOLTRAP spectrometer at ISOLDE-CERN. The new mass of ^{132}Cd offers the first value of the N=82, two-neutron shell gap below Z=50 and confirms the phenomenon of mutually enhanced magicity at ^{132}Sn. Using the recently implemented phase-imaging ion-cyclotron-resonance method, the ordering of the low-lying isomers in ^{129}Cd and their energies are determined. The new experimental findings are used to test large-scale shell-model, mean-field, and beyond-mean-field calculations, as well as the abinitio valence-space in-medium similarity renormalization group.
Highlights
First Glimpse of the N = 82 Shell Closure below Z = 50 from Masses of Neutron-Rich Cadmium Isotopes and Isomers
We probe the N 1⁄4 82 nuclear shell closure by mass measurements of neutron-rich cadmium isotopes with the ISOLTRAP spectrometer at ISOLDE-CERN
The so-called magic numbers of protons and neutrons are associated with large energy gaps in the effective singleparticle spectrum of the nuclear mean field [1], revealing shell closures
Summary
The A ≈ 130 r-process abundance peak has long been considered an indication of a persistent N 1⁄4 82 shell gap in various models. In this Letter, we present the first direct determination of the N 1⁄4 82 shell gap for Z < 50 with mass measurements of exotic cadmium isotopes and isomers between 124Cd and. The neutral products diffused from the ≈2000 °C target into a hot tantalum cavity where the resonance-ionization laser ion source [36] was used to produce singly charged cadmium ions. The ion bunch was injected into the multireflection time-offlight mass spectrometer (MR-TOF MS) [39] where the cadmium ions were separated from contaminants with a resolving power of ≈105. In this Letter, the masses of 131;132Cd were determined with the MR-TOF MS (see Fig. 1) using a two-parameter calibration formula and requiring two reference measurements, as described in [5]. Considering only singly charged ions, the mass mi;x of the ion of interest is related to the masses mi; and mi; of two reference ions by m1i;=x2
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