The $\nu$9/2[404] orbital and the deformation in the A $\sim$ 100 region

W. Urban (1) , J.A. Pinston (1) , J. Genevey (1) , T. Rzaca-Urban , A. Zlomaniec , G.S. Simpson , J.L. Durell , W.R. Phillips , A.G. Smith , B.J. Varley , I. Ahmad , N. Schulz (2)

1 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
2 IReS - Institut de Recherches Subatomiques

A T 1/2 = 16(2) ns isomeric level, populated in the spontaneous fission of $^{248}$Cm, has been found in $^{101}$Zr at 941.8 keV in a measurement of prompt $\gamma$-rays using the EUROGAM2 array. The level is interpreted as a K-isomer corresponding to the 9/2[404] neutron-hole excitation. The quadrupole moment, Q0 = 3.6(4) eb, deduced for the new band indicates a large deformation of $\beta_2$=0.38(4), which is produced by a specific shape-coexistence mechanism. This is another observation of the $\nu$9/2[404] orbital in the mass A $\sim$ 100 region, confirming the presence of the effect reported first in our previous work. The 9/2[404] neutron-hole excitation is also confirmed in the $^{97}$Sr nucleus and the deformation $\beta_2$=0.44(2) is determined for this configuration. The properties of the 9/2[404] neutron orbital and its influence on the onset of deformation in the A $\sim^100 region are discussed.

Mots clés: gamma transitions and level energies; shell model; spontaneous fission

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

W. Urban, J.A. Pinston, J. Genevey, T. Rzaca-Urban, A. Zlomaniec, et al.. The $\nu$9/2[404] orbital and the deformation in the A $\sim$ 100 region. European Physical Journal A, 2004, 22, pp.241-252. ⟨10.1140/epja/i2004-10037-5⟩. ⟨in2p3-00023332⟩