Abstract
Direct proton-knockout reactions of at were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of were investigated through -ray and invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological internucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors, which describe the wave function overlap of the ground state with states in . Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of , valence proton removals populated predominantly the ground state of . This counterintuitive result is attributed to pairing effects leading to a dominance of the ground-state spectroscopic factor. Owing to the ubiquity of the pairing interaction, this argument should be generally applicable to direct knockout reactions from odd-even to even-even nuclei.
- Received 11 January 2021
- Revised 3 March 2021
- Accepted 29 March 2021
DOI:https://doi.org/10.1103/PhysRevLett.126.252501
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