Lifetimes and collectivity of low-lying states in Sn-115

The lifetimes of excited states in Sn-115 have been measured using the Dopp ler shift attenuation method in the reaction Cd-113(alpha,2n gamma) at E-al pha = 27.2 R MeV. Lifetimes were obtained for 18 states and lifetime limits for 6 states with E(x)less than or equal to 4 MeV and J less than or equal to 23/2. The experimentally obtained B(sigma L) values for transitions dee xciting positive-parity states are compared with calculations in the framew ork of the Bardeen-Cooper-Schrieffer quasiparticle model and the interactin g boson fermion model, whereas the values for transitions between negative- parity states are discussed qualitatively within a core-particle coupling p icture. The value of B(E2) = 3.5(11) Weisskopf units (W.u.) for the transit ion linking the 19/2(-) state of the intruder nu h(11/2)pi 2p2h band to the 15/2(-) state of the nu h(11/2)x2(1)(+) multipret strongly supports the co nfiguration nu h(11/2)pi(g(9/2)(-2)g(7/2)(2)) ascribed to this band. [S0556 -2813(99)02904-0].