Nuclear Physics A560 (1993) 633-663 North-Holland NUCLEAR PHYSICS A Decay properties and lifetimes of states in 144Sm from (n, n’r) reaction studies R.A. Gatenby, E.L. Johnson, E.M. Baum, S.W. Yates zyxwvutsrqponmlkjihgfedcbaZYXW Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA D. Wang, J.R. Vanhoy, M.T. McEllistrem Department of Physics, University of Kentucky, Lexington, KY 40506-005, USA T. Belgya, B. Fazekas, G. Molnir Institute of Isotopes, Hungarian Academy of Sciences, H-1525 Budapest, Hungary Received 10 November 1992 (Revised 2 February 1993) Abstract An extensive investigation of ‘“Sm has been carried out with the (n, n’-y) 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 -y-rays, and reduced transition rates have been inferred. Recent shell-model calculations were found to describe the ‘“Sm level scheme very well up to 3.2 MeV. A large number of relatively fast El transitions were observed. Key words: NUCLEAR REACTIONS ‘“Sm (n, n’y), E, = 1.8-4.3 MeV, measured E,, IY, I,(O), E,(O), u(E,); Doppler shift, . ‘“Sm-deduced levels, I, r, branching ratios, 6, Tt,z, B(A); Enriched target; hyperpure Ge detector; Compton suppression. Two-phonon states, shell model 1. Introduction The many similarities between the neighbouring even-even N = 82 nuclei have led to the suggestion [l] that all N = 82 isotones with Z = 58-70 behave as magic nuclei. Two such properties, the presence of low-lying octupole phonons and their large associated B(E3; 3-+ O+) values, prompted a search [2] for two-phonon Correspondence to: Dr. T. Belgya, Radiation Laboratory, Institute of Isotopes, Hungarian Academy of Sciences P.O. Box 77,4-1525 Budapest, Hungary. 0375-9474/93/$06.00 0 1993 - Elsevier Science Publishers B.V. All rights reserved