LIFETIMES AND ELECTROMAGNETIC DECAY PROPERTIES OF NEGATIVE-PARITY STATES IN SM-150, SM-152, SM-154 FROM (N,N'GAMMA) MEASUREMENTS

The Doppler shifts of gamma rays following the decay of the 1(1)- and 3(1)- states in Sm-150, Sm-152, Sm-154 excited by inelastic scattering of 1.3 MeV neutrons from natural Sm2O3 have been measured. With the W interbon theory to describe the slowing down process of the recoiling atoms in the bulk of the target material, nuclear lifetimes could be e xtracted from these data. These measured lifetimes are compared to the results of a recent investigation with the gamma-ray induced Doppler (GRID) broadening technique and have been used to clarify problems ass ociated with the incomplete knowledge of the feeding pattern in heavy nuclei inherent in the GRID method. The large E1 transition rates in S m-152 obtained in the previous study are confirmed; the B(E1) systemat ics has been extended to Sm-154 and is interpreted within the framewor k of the interacting boson model.