Coulomb excitation of Ga73

Abstract

The B(E2;Ii→If) values for transitions in 3171Ga40 and 3173Ga42 were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of Ga71,73 at the REX-ISOLDE on-line isotope mass separator facility. The emitted γ rays were detected by the MINIBALL γ-detector array, and B(E2;Ii→If) values were obtained from the yields normalized to the known strength of the 2⊃+→0⊃+ transition in the Sn120 target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity toward lower excitation energy when adding neutrons beyond N=40. This supports conclusions from previous studies of the gallium isotopes, which indicated a structural change in this isotopic chain between N=40 and 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2⊃- spin and parity for the ground state, the extracted results revealed evidence for a 1/2⊃-,3/2⊃- doublet near the ground state in 3173Ga 42 differing by at most 0.8 keV in energy. © 2010 The American Physical Society.