Structure of ${}^{83}\mathrm{As},$ ${}^{85}\mathrm{As},$ and ${}^{87}\mathrm{As}$: From semimagicity to $\gamma$ softness

K. Rezynkina (1) , D.D. Dao (1) , G. Duchene (1) , J. Dudouet (2) , F. Nowacki (1) , E. Clément (3) , A. Lemasson (3) , C. Andreoiu , A. Astier (4) , G. de Angelis , G. de France (3) , C. Delafosse (4) , I. Deloncle (4) , F. Didierjean (1) , Z. Dombradi , C. Ducoin (2) , A. Gadea , A. Gottardo (4) , D. Guinet (2) , B. Jacquot (3) , P. Jones , T. Konstantinopoulos (4) , I. Kuti , A. Korichi (4) , S.M. Lenzi , G. Li , F. Le Blanc (1, 4) , C. Lizarazo , R. Lozeva (1, 4) , G. Maquart (2) , B. Million , C. Michelagnoli (3, 5) , D.R. Napoli , A. Navin (3) , R.M. Perez-Vidal , C.M. Petrache (4) , N. Pietralla , D. Ralet , M. Ramdhane (6) , M. Rejmund (3) , O. Stezowski (2) , C. Schmitt (1, 3) , D. Sohler , D. Verney (4)

1 IPHC - Institut Pluridisciplinaire Hubert Curien
2 IP2I Lyon - Institut de Physique des 2 Infinis de Lyon
3 GANIL - Grand Accélérateur National d'Ions Lourds
4 IJCLab - Laboratoire de Physique des 2 Infinis Irène Joliot-Curie
5 ILL - Institut Laue-Langevin
6 LPSC - Laboratoire de Physique Subatomique et de Cosmologie

The structure of ${}^{83}\mathrm{As}$, ${}^{85}\mathrm{As}$, and ${}^{87}\mathrm{As}$ have been studied in fusion-fission reaction ${}^{238}\mathrm{U}+{}^9\mathrm{Be}$. Fission fragments were identified in mass and atomic number using the VAMOS$++$ spectrometer and the coincident $\gamma$ rays were detected in the $\gamma$-ray tracking array AGATA. New transitions in ${}^{83}\mathrm{As}$ and ${}^{85}\mathrm{As}$ are reported and placed in the level schemes. A level scheme of the excited states in ${}^{87}\mathrm{As}$ is proposed for the first time. The data are interpreted in frame of large-scale shell-model calculations, SU3 symmetries, and beyond mean-field frameworks. A spherical regime at magic number $N=50$ is predicted and the location of the proton $g_{9/2}$ orbital is proposed for the first time. Development of collectivity in a prolate deformed, $\gamma$-soft regime in the open shell cases ${}^{85}\mathrm{As}$ and ${}^{87}\mathrm{As}$, most neutron-rich isotopes beyond $N=50$, is concluded. Data and theoretical calculations give confidence to a relatively high extrapolated excitation energy about 4 MeV of the $9/2^{+}$ state in ${}^{79}\mathrm{Cu}$, one proton above ${}^{78}\mathrm{Ni}$.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

K. Rezynkina, D.D. Dao, G. Duchene, J. Dudouet, F. Nowacki, et al.. Structure of ${}^{83}\mathrm{As},$ ${}^{85}\mathrm{As},$ and ${}^{87}\mathrm{As}$: From semimagicity to $\gamma$ softness. Phys.Rev.C, 2022, 106 (1), pp.014320. ⟨10.1103/PhysRevC.106.014320⟩. ⟨hal-03626020⟩