Precision mass measurements of $^{67}$Fe and $^{69,70}$Co : Nuclear structure toward N=40 and impact on r -process reaction rates

L. Canete , S. Giraud (1) , A. Kankainen , B. Bastin (1) , F. Nowacki (2) , A. Poves , P. Ascher (3) , T. Eronen , V. Alcindor (1) , A. Jokinen , A. Khanam , I.D. Moore , D. Nesterenko , Francois de Oliveira Santos (1) , H. Penttilä , C. Petrone , I. Pohjalainen , A. de Roubin , V. A Rubchenya , M. Vilen , J. Äystö

1 GANIL - Grand Accélérateur National d'Ions Lourds
2 IPHC - Institut Pluridisciplinaire Hubert Curien
3 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan

Accurate mass measurements of neutron-rich iron and cobalt isotopes Fe67 and Co69,70 have been realized with the JYFLTRAP double Penning-trap mass spectrometer. With novel ion-manipulation techniques, the masses of the Co69,70 ground states and the 1/2− isomer in Co69 have been extracted for the first time. The measurements remove ambiguities in the previous mass values and yield a smoother trend on the mass surface, extending it beyond N=40. The moderate N=40 subshell gap has been found to weaken below Ni68, a region known for shape coexistence and increased collectivity. The excitation energy for the 1/2− intruder state in Co69 has been determined for the first time and is compared to large-scale shell-model calculations. The new mass values also reduce significantly mass-related uncertainties for the astrophysical rapid neutron-capture process calculations.

Mots clés: Nuclear Structure

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

L. Canete, S. Giraud, A. Kankainen, B. Bastin, F. Nowacki, et al.. Precision mass measurements of $^{67}$Fe and $^{69,70}$Co : Nuclear structure toward N=40 and impact on r -process reaction rates. Physical Review C, 2020, 101 (4), pp.041304. ⟨10.1103/PhysRevC.101.041304⟩. ⟨hal-03012793⟩