Yrast 6 seniority isomers of Sn

Simpson, G. S.*; Gey, G.*; Jungclaus, A.*; Taprogge, J.*; Nishimura, Shunji*; Sieja, K.*; Doornenbal, P.*; Lorusso, G.*; Sderstrm, P.-A.*; Sumikama, Toshiyuki*; Xu, Z. Y.*; Baba, Hidetada*; Browne, F.*; Fukuda, Naoki*; Inabe, Naoto*; Isobe, T.*; Jung, H. S.*; Kameda, Daisuke*; Kim, G. D.*; Kim, Y.-K.*; Kojouharov, I.*; Kubo, Toshiyuki*; Kurz, N.*; Kwon, Y. K.*; Li, Z.*; Sakurai, Hiroyoshi*; Schaffner, H.*; Shimizu, Y.*; Suzuki, H.*; Takeda, H.*; Vajta, Zs.*; Watanabe, H.*; Wu, J.*; Yagi, A.*; Yoshinaga, Kenta*; Bnig, S.*; Daugas, J.-M.*; Drouet, F.*; Gernhuser, R.*; Ilieva, S.*; Krll, T.*; Montaner-Piz, A.*; Moschner, K.*; Mcher, D.*; Nadja, H.*; Nishibata, Hiroki*; Nowacki, F.*; Odahara, Atsuko*; Orlandi, R.  ; Steiger, K.*; Wendt, A.*

Delayed -ray cascades, originating from the decay of 6 isomeric states, in the very neutron-rich, semimagic isotopes Sn were observed following the projectile fission of a U beam at RIBF, RIKEN. The wave functions of these isomeric states are proposed to be predominantly a fully aligned pair of f neutrons. Shell-model calculations, performed using a realistic effective interaction, reproduce well the energies of the excited states of these nuclei and the measured transition rates, with the exception of the 2;6) rate of Sn, which deviates from a simple seniority scheme. Empirically reducing the orbit matrix elements produces a 4+1 state with almost equal seniority 2 and 4 components, correctly reproducing the experimental 2;6) rate of Sn. These data provide a key benchmark for shell-model interactions far from stability.