Decay Properties And Lifetimes Of States In Sm-144 From (N, N'Gamma) Reaction Studies

An extensive investigation of Sm-144 has been carried out with the (n, n'gamma) reaction. Gamma-ray excitation function and angular-distribution measurements were performed at neutron energies up to 4.3 MeV. Many new levels have been established and characterized, and the assignments of several previously known states have been clarified. Level lifetimes were measured following the inelastic neutron-scattering reaction by observing the Doppler shifts of de-exciting gamma-rays, and reduced transition rates have been inferred. Recent shell-model calculations were found to describe the Sm-144 level scheme very well up to 3.2 MeV. A large number of relatively fast E1 transitions were observed.