Precision Mass Measurement of Proton-Dripline Halo Candidate ²²Al

2023/12/18 by Campbell, S. E., Bollen, G., Brown, B. A. +12 · 1 citation
#FOS: Physical sciences #Nuclear Experiment (nucl-ex)

paper · doi:10.48550/arxiv.2312.11366

Abstract

We report the first mass measurement of the proton-halo candidate ²²Al performed with the LEBIT facility's 9.4~T Penning trap mass spectrometer at FRIB. This measurement completes the mass information for the lightest remaining proton-dripline nucleus achievable with Penning traps. ²²Al has been the subject of recent interest regarding a possible halo structure from the observation of an exceptionally large isospin asymmetry [Phys. Rev. Lett. 125 192503 (2020)]. The measured mass excess value of ME=18 093.6(7)~keV, corresponding to an exceptionally small proton separation energy of S_p = 99.2(1.0)~keV, is compatible with the suggested halo structure. Our result agrees well with predictions from sd-shell USD Hamiltonians. While USD Hamiltonians predict deformation in ²²Al ground-state with minimal 1s_1/2 occupation in the proton shell, a particle-plus-rotor model in the continuum suggests that a proton halo could form at large quadrupole deformation. These results emphasize the need for a charge radius measurement to conclusively determine the halo nature.

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• A high-voltage MR-ToF mass spectrometer and separator for the study of exotic isotopes at FRIB

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