Evolution of deformation in neutron-rich Ba isotopes up to $A=150$

R. Lică , G. Benzoni , T.R. Rodríguez , M.J.G. Borge , L.M. Fraile , H. Mach , A.I. Morales , M. Madurga , C.O. Sotty , V. Vedia , H. de Witte , J. Benito , R.N. Bernard (1) , T. Berry , A. Bracco , F. Camera , S. Ceruti , V. Charviakova , N. Cieplicka-Oryńczak , C. Costache , F.C.L. Crespi , J. Creswell , G. Fernandez-Martínez , H. Fynbo , P.T. Greenlees , I. Homm , M. Huyse , J. Jolie , V. Karayonchev , U. Köster (2) , J. Konki , T. Kröll , J. Kurcewicz , T. Kurtukian-Nieto (3) , I. Lazarus , M.V. Lund , N. Mărginean , R. Mărginean , C. Mihai , R.E. Mihai , A. Negret , A. Orduz , Z. Patyk , S. Pascu , V. Pucknell , P. Rahkila , E. Rapisarda , J.M. Regis , L.M. Robledo , F. Rotaru , N. Saed-Samii , V. Sánchez-Tembleque , M. Stanoiu , O. Tengblad , M. Thuerauf , A. Turturica , P. van Duppen , N. Warr

1 DAM - Direction des Applications Militaires
2 ILL - Institut Laue-Langevin
3 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan

The occurrence of octupolar shapes in the Ba isotopic chain was recently established experimentally up to $N=90$. To further extend the systematics, the evolution of shapes in the most neutron-rich members of the $Z=56$ isotopic chain accessible at present, $^{148,150}$Ba, has been studied via $\beta$ decay at the ISOLDE Decay Station. This paper reports on the first measurement of the positive- and negative-parity low-spin excited states of $^{150}$Ba and presents an extension of the $\beta$-decay scheme of $^{148}$Cs. Employing the fast timing technique, half-lives for the $2_1^+$ level in both nuclei have been determined, resulting in $T_{1/2}=1.51(1)$ ns for $^{148}$Ba and $T_{1/2}=3.4(2)$ ns for $^{150}$Ba. The systematics of low-spin states, together with the experimental determination of the $B(E2:2^+ \rightarrow 0^+$) transition probabilities, indicate an increasing collectivity in $^{148–150}$Ba, towards prolate deformed shapes. The experimental data are compared to symmetry conserving configuration mixing (SCCM) calculations, confirming an evolution of increasingly quadrupole deformed shapes with a definite octupolar character.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

R. Lică, G. Benzoni, T.R. Rodríguez, M.J.G. Borge, L.M. Fraile, et al.. Evolution of deformation in neutron-rich Ba isotopes up to $A=150$. Phys.Rev.C, 2018, 97 (2), pp.024305. ⟨10.1103/PhysRevC.97.024305⟩. ⟨hal-01714259⟩