Suppressed electric quadrupole collectivity in Si 32

Heery, J. (ORCID:0000000230239907); Henderson, J. (ORCID:0000000260109644); Hoffman, C. R. (ORCID:0000000171419827); Hill, A. M. (ORCID:0000000303175511); Beck, T. (ORCID:0000000253959421); Cousins, C. (ORCID:0009000838558217); Farris, P.; Gade, A.; Gillespie, S. A. (ORCID:000000019268518X); Holt, J. D.; Hu, B.; Iwasaki, H. (ORCID:000000030750380X); Kisyov, S.; Kuchera, A. N. (ORCID:0000000188107993); Longfellow, B.; Müller-Gatermann, C. (ORCID:0000000291815568); Poves, A.; Rubino, E. (ORCID:0000000264227015); Russell, R. (ORCID:0000000165800111); Salinas, R. (ORCID:0000000236250920); Sanchez, A. (ORCID:0000000239134677); Weisshaar, D. (ORCID:0000000291903971); Wu, C. Y. (ORCID:0000000157727196); Wu, J.

doi:10.1103/physrevc.109.014327

Home/Archive/DOE OSTI

DOE OSTI · 2282817

Suppressed electric quadrupole collectivity in Si 32

View original source ↗Export metadata ↓

Abstract

Lying between O 16 and Ca 40 , the s d shell is well described by robust phenomenological and nuclear theories. In this work, however, we highlight an unexplained reduction in electric-quadrupole strength in the rare isotope Si 32 , studied through sub-barrier Coulomb excitation. It is found that the oblate nature of the deformation is well reproduced, while the absolute scale of quadrupole deformation, however, is inhibited by approximately a factor of 2 compared to theoretical predictions. Through comparison with shell-model and calculations, we present a number of possible explanations for this inhibited E 2 strength. By comparing the results of these calculations to multiple observables, we conclude that there is a reduced role for out-of-space excitations in Si 32 , resulting in a reduction in the corrections normally applied to both models. Published by the American Physical Society 2024

Explore related subjects

20 ≤ A ≤ 38 73 NUCLEAR PHYSICS AND RADIATION PHYSICS Ab initio calculations Collective levels Coulomb excitation Electromagnetic transitions Multipole matrix elements Radioactive beams Shell model Spectroscopic factors & electromagnetic moments

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Heery, J. (ORCID:0000000230239907), Henderson, J. (ORCID:0000000260109644), Hoffman, C. R. (ORCID:0000000171419827), Hill, A. M. (ORCID:0000000303175511), Beck, T. (ORCID:0000000253959421), Cousins, C. (ORCID:0009000838558217), Farris, P., Gade, A., Gillespie, S. A. (ORCID:000000019268518X), Holt, J. D., Hu, B., Iwasaki, H. (ORCID:000000030750380X), Kisyov, S., Kuchera, A. N. (ORCID:0000000188107993), Longfellow, B., Müller-Gatermann, C. (ORCID:0000000291815568), Poves, A., Rubino, E. (ORCID:0000000264227015), Russell, R. (ORCID:0000000165800111), Salinas, R. (ORCID:0000000236250920), Sanchez, A. (ORCID:0000000239134677), Weisshaar, D. (ORCID:0000000291903971), Wu, C. Y. (ORCID:0000000157727196), Wu, J.. 2024-01-25. Suppressed electric quadrupole collectivity in Si 32. https://doi.org/10.1103/physrevc.109.014327

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related reports

DOE OSTI2026

Measurement of the Ground State Spin and Parity of 22 Al Disfavors Halo Formation

We report the decisive resolution of the ground state spin and parity of the proton–drip line nucleus 22 Al, 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 22 Mg to the 18 Ne ground state. This observation uniquely fixes the 22 Al 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 22 Al.

20 ≤ A ≤ 38↗

DOE OSTI2026

Probing the 𝑗 dependence of angular distributions and 𝑁=20 shell rigidity via the 36 S (𝑝,𝑑) 35 S reaction

An investigation of the N=20 36 S nucleus has been performed through a detailed study of the 3 6S (p,d)3 5S neutron-removal reaction, employing a 66-MeV proton beam at iThemba Laboratory for Accelerator Based Sciences and an innovative target design. Using the high-resolution K = 600 magnetic spectrometer, 98 states in 3 5S were identified up to 16-MeV excitation energy, including 47 previously unobserved states. Angular distributions and spectroscopic factors, including isobaric analog-state contributions, were extracted for 81 levels. A pronounced j dependence in the angular distributions of ℓ=2 states provides refined insights into the spin-orbit splitting. Finite-range adiabatic distorted-wave approximation calculations qualitatively reproduce the observed j dependence. Comparisons of the measured 1d 5/2 spectroscopic strength distribution with large-scale shell-model and ab initio calculations show good agreement overall, and the robustness of the N=20 shell closure in 36 S is confirmed when comparing the relatively low fp orbital occupancies in 40 Ca and 3 6S across the Fermi surface. This study underscores the utility of neutron-removal reactions in probing nuclear structure and the Fermi surface of sd nuclei and beyond. The findings advance our understanding of shell evolution and offer constraining data for theoretical models.

20 ≤ A ≤ 38↗

DOE OSTI2025

Clarifying the 𝑁,𝑍 = 14 Shells near the Drip Lines from the Spectroscopy of 22 Si and 21 Al

Evidence for a (sub)-shell closure at 𝑍 = 14 has been observed from the spectroscopy of 22 Si and 21 Al . Using a fast 23 Si beam on a 9 Be target, several proton-decaying resonances have been populated in 21 Al and 22 Si , including the first measurement of the 2$^{+}_{1}$ state in 22 Si with an excitation energy of 2.352(55) MeV. Relative to the known 𝑁 = 14 subshell closure in 22 O , the 22 Si 2$^{+}_{1}$ excitation energy indicates the existence of a weakened 𝑍 = 14 subshell closure. To reproduce the new spectroscopic information and known 22 Al levels, the energy of the 1⁢𝑠 1/2 orbit must be substantially decreased, which imparts Thomas-Ehrman shifts to all excited states observed in the present Letter and explains the structure of nuclei in the 𝑠⁢𝑑 shell for this region of the proton drip line.

20 ≤ A ≤ 38↗