Measurement of the Ground State Spin and Parity of Al22 Disfavors Halo Formation
Artikel i vetenskaplig tidskrift, 2026
We report the decisive resolution of the ground state spin and parity of the proton–drip line nucleus Al22, a prime candidate for a proton halo. The resolution stems from the first β-delayed charged particle emission experiment in the gas stopping area at the Facility for Rare Isotope Beams (FRIB), leveraging high-intensity, low-energy beams extracted from the Advanced Cryogenic Gas Stopper (ACGS). The pristine beam quality from FRIB and the ACGS enabled a sensitive particle identification technique using thin silicon detectors, allowing for the suppression of the dominant proton background and the first observation of the weak β-delayed α transition from the isobaric analog state in Mg22 to the Ne18 ground state. This observation uniquely fixes the Al22 ground state as 4+. The valence proton is confined by a dominant d-wave centrifugal barrier which, combined with the Coulomb repulsion, hinders the tunneling required for halo formation despite the exceptionally low proton separation energy of Al22
Författare
Erik Asbjörn Mikkelsen Jensen
Aarhus Universitet
Chalmers, Fysik, Subatomär, högenergi- och plasmafysik
J. S. Nielsen
Aarhus Universitet
B. S.O. Johansson
Aarhus Universitet
A. Adams
Michigan State University
J. Dopfer
Michigan State University
C. S. Sumithrarachchi
Michigan State University
L. J. Sun
Michigan State University
L. E. Weghorn
Michigan State University
Tyler Wheeler
Michigan State University
C. Wrede
Michigan State University
M. Borge
Consejo Superior de Investigaciones Científicas (CSIC)
O. Tengblad
Consejo Superior de Investigaciones Científicas (CSIC)
M. Madurga
University of Tennessee
Björn Jonson
Chalmers, Fysik, Subatomär, högenergi- och plasmafysik
K. Riisager
Aarhus Universitet
H. O. U. Fynbo
Aarhus Universitet
Physical Review Letters
0031-9007 (ISSN) 1079-7114 (eISSN)
Vol. 136 20 202503Atomkärnor som knappt existerar
Vetenskapsrådet (VR) (2022-04248), 2023-01-01 -- 2026-12-31.
Ämneskategorier (SSIF 2025)
Subatomär fysik
DOI
10.1103/3lpm-sy41