Rotational Feshbach resonances in the deformed halo nucleus ³¹Ne

@misc{watanabe2026rotational,
  title = {{Rotational Feshbach resonances in the deformed halo nucleus $^31$Ne}},
  author = {Shin Watanabe and Shoya Ogawa and Takuma Matsumoto and Kazuyuki Ogata},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.04758},
  eprint = {2609.04758},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.04758},
}

TY  - UNPB
TI  - Rotational Feshbach resonances in the deformed halo nucleus ^31Ne
AU  - Shin Watanabe
AU  - Shoya Ogawa
AU  - Takuma Matsumoto
AU  - Kazuyuki Ogata
PY  - 2026
DA  - 2026/09/04
PB  - arXiv
DO  - 10.48550/arxiv.2609.04758
UR  - https://arxiv.org/abs/2609.04758
AB  - Background: The deformed halo nucleus ^31Ne exhibits unique structural properties arising from the interplay between its halo neutron and the deformation of the ^30Ne core. While previous studies have established the nature of its weakly-bound ground state through reaction cross sections and inclusive breakup measurements, the structure of its excited states in the low-energy continuum, which are expected to appear as resonances, remains largely unexplored. Purpose: We investigate the structure of these resonant states and clarify their rotational nature and formation mechanism. Method: The structure of ^31Ne is described using the particle rotor model (PRM), which explicitly treats the coupling between core excitation and single-particle motion in both bound and continuum states. Results: The calculations predict the emergence of unbound rotational states in the low-energy continuum of ^31Ne, which form a rotational sequence built on the weakly-bound Nilsson [321 3/2] configuration. As the total angular momentum increases along the rotational band, the intrinsic Nilsson structure is largely preserved, whereas the dominant core-spin component shifts to higher spins. These resonances are stabilized through the combined effects of coupling to higher-lying closed core-excited channels and reduced effective neutron relative energies, and can therefore be interpreted as rotational Feshbach resonances. Conclusion: The present study elucidates the formation mechanism of rotational Feshbach resonances in ^31Ne. This mechanism is expected to be a general feature of weakly-bound deformed nuclei. Exclusive breakup measurements with coincident detection of γ rays from the de-exciting core will provide crucial tests of the proposed formation mechanism of rotational Feshbach resonances.
ER  -