Fast-timing study of the -forbidden 1/2 3/2 transition in Sn

Lic, R.*; Mach, H.*; Fraile, L. M.*; Gargano, A.*; Borge, M. J. G.*; Mrginean, N.*; Sotty, C. O.*; Vedia, V.*; Andreyev, A. N.; Benzoni, G.*; Bomans, P.*; Borcea, R.*; Coraggio, L.*; Costache, C.*; De Witte, H.*; Flavigny, F.*; Fynbo, H.*; Gaffney, L. P.*; Greenlees, P. T.*; Harkness-Brennan, L. J.*; Huyse, M.*; Ibez, P.*; Judson, D. S.*; Konki, J.*; Korgul, A.*; Krll, T.*; Kurcewicz, J.*; Lalkovski, S.*; Lazarus, I.*; Lund, M. V.*; Madurga, M.*; Mrginean, R.*; Marroqun, I.*; Mihai, C.*; Mihai, R. E.*; Morales, A. I.*; Ncher, E.*; Negret, A.*; Page, R. D.*; Pakarinen, J.*; Pascu, S.*; Paziy, V.*; Perea, A.*; Prez-Liva, M.*; Picado, E.*; Pucknell, V.*; Rapisarda, E.*; Rahkila, P.*; Rotaru, F.*; Swartz, J. A.*; Tengblad, O.*; Van Duppen, P.*; Vidal, M.*; Wadsworth, R.*; Walters, W. B.*; Warr, N.*

The levels in Sn populated from the decay of In isomers were investigated at the ISOLDE facility of CERN using the newly commissioned ISOLDE Decay Station. The lowest 1/2 state and the 3/2 ground state in Sn are expected to have configurations dominated by the neutron (=0) and (=2) single-particle states, respectively. Consequently, these states should be connected by a somewhat slow -forbidden transition. Using fast-timing spectroscopy we have measured the half-life of the 1/2 315.3-keV state, = 19(10) ps, which corresponds to a moderately fast transition. Shell-model calculations using the CD-Bonn effective interaction, with standard effective charges and factors, predict a 4-ns half-life for this level. We can reconcile the shell-model calculations to the measured value by the renormalization of the effective operator for neutron holes.