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Nuclear shape and structure in neutron-rich 110,111Tc

  • Author(s): Luo, Y.X.
  • Hamilton, J.H.
  • Rasmussen, J.O.
  • Ramayya, A.V.
  • Stefanescu, I.
  • Hwang, J.K.
  • Zhu, S.J.
  • Gore, P.M.
  • Jones, E.F.
  • Fong, D.
  • Wu, S.C.
  • Lee, I.Y.
  • Ginter, T.N.
  • Ter-Akopian, G.M.
  • Daniel, A.V.
  • Stoyer, M.A.
  • Donangelo, R.
  • Gelberg, A.
  • et al.
Abstract

The structure of Tc nuclei is extended to the more neutron-rich regions based on measurements of prompt gamma rays from the spontaneous fission of 252Cf at Gammasphere. The level scheme of N=67 neutron-rich (Z=43) 110Tc is established for the first time and that of 111Tc is expanded. The ground-state band of 111Tc reaches the band-crossing region and the new observation of the weakly populated alpha = -1/2 member of the band provides important information of signature splitting. The systematics of band crossings in the isotopic and isotonic chains and a CSM calculation suggest that the band crossing of the gs band of 111Tc is due to alignment of a pair of h11/2 neutrons. The best fit to signature splitting, branching ratios, and excitations of the ground-state band of 111Tc by RTRP model calculations result in a shape of epsilon2 = 0.32 and gamma = -26 deg. for this nucleus. Its triaxiality is larger than that of 107Tc, to indicate increasing triaxiality with increasing neutron number. The identification of the weakly-populated "K+2 satellite" band provides strong evidence for the large triaxiality of 111Tc. In 110Tc the four lowest-lying levels observed are very similar to those in 108Tc. At an excitation of 478.9 keV above the lowest state observed, ten states of a delta I = 1 band are observed. This band is very analogous to the delta I = 1 bands in 106,108Tc, but it has greater signature splitting at higher spins.

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