Neutron core excitations in the N=126 nuclide Po210

Excited states above the 16(+) isomer in Po-210 have been identified using time-correlated gamma-ray spectroscopy techniques and the Hg-204(C-13, 3n alpha) Po-210 reaction. States up to similar to 27h have been identified, including an isomer at 8074 keV with a mean life of 13(2) ns. Among the new states, a candidate for the 17(+) state obtained from maximal coupling of the pi[h(9/2)i(13/2)](11)- valence proton configuration and the nu[p(1/2)(-1)i(11/2)](6-) neutron core excitation has been identified. This and other results are compared with semiempirical shell-model calculations that predict that single core excitations from the i(13/2) neutron orbital and double core excitations out of the p(1/2) and f(5/2) orbitals, populating the g(9/2), i(11/2), and j(15/2) orbitals above the N = 126 shell, will compete in energy. Good agreement is obtained for the lower states but there are systematic discrepancies at high spins including the absence of states that are calculated to lie low in the spectrum, implying uncertainties for configurations associated either with the i(13/2) neutron hole or double core excitations.