Lifetimes and electromagnetic decay properties of negative-parity states in [sup 150,152,154]Sm from ([ital n],[ital n][prime][gamma]) measurements

The Doppler shifts of [gamma] rays following the decay of the 1[sub 1][sup [minus]] and 3[sub 1][sup [minus]] states in [sup 150,152,154]Sm excited by inelastic scattering of 1.3 MeV neutrons from natural Sm[sub 2]O[sub 3] have been measured. With the Winterbon theory to describe the slowing down process of the recoiling atoms in the bulk of the target material, nuclear lifetimes could be extracted 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 associated with the incomplete knowledge of the feeding pattern in heavy nuclei inherent in the GRID method. The large [ital E]1 transition rates in [sup 152]Sm obtained in the previous study are confirmed; the [ital B]([ital E]1) systematics has been extended to [sup 154]Sm and is interpreted within the framework of the interacting boson model.