I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Fragmentation of single-particle strength around the doubly-magicnucleus 132 Sn and the position of the 0f5/2 proton-hole state in 131 In†
V. Vaquero,∗1 A. Jungclaus,∗1 T. Aumann,∗2,∗3 J. Tscheuschner,∗2 E. V. Litvinova,∗4 J. A. Tostevin,∗5H. Baba,∗6 D. S. Ahn,∗6 R. Avigo,∗7,∗8 K. Boretzky,∗3 A. Bracco,∗7,∗8 C. Caesar,∗2,∗3 F. Camera,∗7,∗8S. Chen,∗9,∗6 V. Derya,∗10 P. Doornenbal,∗6 J. Endres,∗10 N. Fukuda,∗6 U. Garg,∗11 A. Giaz,∗7
M. N. Harakeh,∗3,∗12 M. Heil,∗3 A. Horvat,∗2 K. Ieki,∗13,∗6 N. Imai,∗14 N. Inabe,∗6 N. Kalantar-Nayestanaki,∗12
N. Kobayashi,∗14,∗6 Y. Kondo,∗15,∗6 S. Koyama,∗14,∗6 T. Kubo,∗6 I. Martel,∗16 M. Matsushita,∗17 B. Million,∗8T. Motobayashi,∗6 T. Nakamura,∗15,∗6 N. Nakatsuka,∗6,∗2 M. Nishimura,∗6 S. Nishimura,∗6 S. Ota,∗17 H. Otsu,∗6T. Ozaki,∗15,∗6 M. Petri,∗2 R. Reifarth,∗18 J. L. Rodríguez-Sánchez,∗19,∗3 D. Rossi,∗2 A. T. Saito,∗15,∗6H. Sakurai,∗6,∗14 D. Savran,∗3 H. Scheit,∗2 F. Schindler,∗2,∗3 P. Schrock,∗2 D. Semmler,∗2 Y. Shiga,∗13,∗6M. Shikata,∗15,∗6 Y. Shimizu,∗6 H. Simon,∗3 D. Steppenbeck,∗6 H. Suzuki,∗6 T. Sumikama,∗6 D. Symochko,∗2I. Syndikus,∗2 H. Takeda,∗6 S. Takeuchi,∗6 R. Taniuchi,∗14,∗6 Y. Togano,∗15,∗6 J. Tsubota,∗15,∗6 H. Wang,∗6O. Wieland,∗8 K. Yoneda,∗6 J. Zenihiro,∗6 and A. Zilges∗10The neutron-hole and proton-hole nuclei 131 Sn andIn were studied using one-nucleon removal reactionsfrom doubly-magic 132 Sn at relativistic energies. In131In, a 2910(50)-keV γ ray was observed for the firsttime, see Fig. 1, mainly thanks to the good energy andtime resolution of the eight LaBr3 detectors employedin this experiment. This high-energy γ ray was tentatively assigned to the decay of the 0f5/2 proton-holestate to the known 1/2− level at 365 keV. Thus, theexcitation energy of the last so far unknown protonhole state in 132 Sn was fixed to 3275(50) keV. From theabsolute intensities of the observed γ rays, the spectroscopic factors for the 1d5/2 and 0g7/2 neutron-holestates in 131 Sn and the 1p3/2 and 0f5/2 proton-holestates in 131 In were determined. They nicely agreewith those of the analog states with quantum numbersn(ℓ + 1)j+1 in 207 Pb and 207 Tl indicating that the close
resemblance between the shell structures around thedoubly-magic nuclei 132 Sn and 208 Pb established sincelong also holds for the spectroscopic factors. To investigate the origin of the strong fragmentation of singleparticle strength state-of-the-art calculations based on131

Condensed from the article in Phys. Rev. Lett. 124, 022501(2020)∗1 Instituto de Estructura de la Materia, CSIC
∗2 Institut für Kernphysik, TU Darmstadt∗3 GSI Helmholtzzentrum für Schwerionenforschung GmbH
∗4 Department of Physics, Western Michigan University∗5 Department of Physics, University of Surrey∗6 RIKEN Nishina Center∗7 Dipartimento di Fisica dell’Università degli Studi di Milano∗8 INFN, Sezione di Milano∗9 School of Physics and State Key Laboratory of Nuclear
Physics and Technology, Peking University∗10 Institut für Kernphysik, Universität zu Köln
∗11 Department of Physics, University of Notre Dame
∗12 KVI-CART∗13 Department of Physics, Rikkyo University∗14 Department of Physics, The University of Tokyo∗15 Department of Physics, Tokyo Institute of Technology∗16 Departamento de Fsica Aplicada, Universidad de Huelva∗17 Center for Nuclear Study, The University of Tokyo∗18 Institut für Kernphysik, Goethe University Frankfurt∗19 Universidad de Santiago de Compostela†

Fig. 1. Doppler-corrected γ-ray spectra of 131 In populated
via one-proton removal from 132 Sn measured with a) 96
NaI crystals of DALI2 covering polar angles in the range
θ = 50–150◦ and b) eight LaBr3 detectors placed at θ =30◦ (adopted from Fig. 1 of the original article).

the relativistic particle-vibration coupling model wereperformed. While the coupling to the first excited 3−states in the core nuclei 132 Sn and 208 Pb was identified
as the main origin for the reduced spectroscopic factors
measured for the 1d5/2 /1f7/2 single-particle states in
131
Sn/207 Pb and the 1p3/2 /1d5/2 levels in 131 In/207 Tl,
clearly more complex coupling scenarios are responsible
for the strong fragmentation and the small measured
spectroscopic factors in the case of the 0g7/2 /0h9/2
states in 131 Sn/207 Pb and the 0f5/2 /0g7/2 levels in131
In/207 Tl.

- S16 -1