Measurement of the Sign of the Spectroscopic Quadrupole Moment for the 2+1 State in 70Se: No Evidence for Oblate Shape

Phys. Rev. Lett.

98
072501
(2007)
A.M. Hurst, P.A. Butler, D.G. Jenkins, P. Delahaye, F. Wenander, F. Ames, C.J. Barton, T. Behrens, A. Bürger, J. Cederkäll, E. Clément, T. Czosnyka, T. Davinson, G. De Angelis, J. Eberth, A. Ekström, S. Franchoo, G. Georgiev, A. Görgen, R.-D. Herzberg, M. Huyse, O. Ivanov, J. Iwanicki, G.D. Jones, P. Kent, U. Köster, T. Kröll, R. Krücken, A.C. Larsen, M. Nespolo, M. Pantea, E.S. Paul, M. Petri, H. Scheit, T. Sieber, S. Siem, J.F. Smith, A. Steer, I. Stefanescu, N.U.H. Syed, J. Van De Walle, P. Van Duppen, R. Wadsworth, N. Warr, D. Weißhaar, M. Zielińska

Using a method whereby molecular and atomic ions are independently selected, an isobarically pure beam of  
70
 Se 
  ions was postaccelerated to an energy of 206 MeV using REX-ISOLDE. Coulomb-excitation yields for states in the beam and target nuclei were deduced by recording deexcitation 𝛾 rays in the highly segmented MINIBALL 𝛾-ray spectrometer in coincidence with scattered particles in a silicon detector. At these energies, the Coulomb-excitation yield for the first 2+ state is expected to be strongly sensitive to the sign of the spectroscopic quadrupole moment through the nuclear reorientation effect. Experimental evidence is presented here for a prolate shape for the first 2+ state in  
70
 Se 
 , reopening the question over whether there are, as reported earlier, deformed oblate shapes near to the ground state in the light selenium isotopes.

DOI
10.1103/PhysRevLett.98.072501
Published on
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