Two-neutron knockout as a probe of the composition of states in Mg 22, Al 23, and Si 24

B. Longfellow, A. Gade, J. A. Tostevin, E. C. Simpson, B. A. Brown, A. Magilligan, D. Bazin, P. C. Bender, M. Bowry, B. Elman, E. Lunderberg, D. Rhodes, M. Spieker, D. Weisshaar, S. J. Williams

    Research output: Contribution to journalArticlepeer-review

    15 Citations (Scopus)

    Abstract

    Simpson and Tostevin proposed that the width and shape of exclusive parallel momentum distributions of the A-2 residue in direct two-nucleon knockout reactions carry a measurable sensitivity to the nucleon single-particle configurations and their couplings within the wave functions of exotic nuclei. We report here on the first benchmarks and use of this new spectroscopic tool. Exclusive parallel momentum distributions for states in the neutron-deficient nuclei Mg22,Al23, and Si24 populated in such direct two-neutron removal reactions were extracted and compared to predictions combining eikonal reaction theory and shell-model calculations. For the well-known Mg22 and Al23 nuclei, measurements and calculations were found to agree, supporting the dependence of the parallel momentum distribution width on the angular momentum composition of the shell-model two-neutron amplitudes. In Si24, a level at 3439(9) keV, of relevance for the important Al23(p,γ)Si24 astrophysical reaction rate, was confirmed to be the 22+ state, whereas the 41+ state, expected to be strongly populated in two-neutron knockout, was not observed. This puzzle is resolved by theoretical considerations of the Thomas-Ehrman shift, which also suggests that a previously reported 3471-keV state in Si24 is, in fact, the (02+) level with one of the largest experimental mirror-energy shifts ever observed.

    Original languageEnglish
    Article number031303
    JournalPhysical Review C
    Volume101
    Issue number3
    DOIs
    Publication statusPublished - Mar 2020

    Fingerprint

    Dive into the research topics of 'Two-neutron knockout as a probe of the composition of states in Mg 22, Al 23, and Si 24'. Together they form a unique fingerprint.

    Cite this