Lifetime measurement for the 2 1 + state in 140 Sm and the onset of collectivity in neutron-deficient Sm isotopes

F. L. Bello Garrote,1 A. Görgen,1 J. Mierzejewski,2 C. Mihai,3 J. P. Delaroche,4 M. Girod,4 J. Libert,4 E. Sahin,1 J. Srebrny,2 T. Abraham,2 T. K. Eriksen,1 F. Giacoppo,1 T. W. Hagen,1 M. Kisielinski,2 M. Klintefjord,1 M. Komorowska,2 M. Kowalczyk,2 A. C. Larsen,1 T. Marchlewski,2 I. O. Mitu,3 S. Pascu,3 S. Siem,1 A. Stolarz,2 and T. G. Tornyi1,5 1Department of Physics, University of Oslo, N-0316 Oslo, Norway 2Heavy Ion Laboratory, University of Warsaw, PL-02-093 Warsaw, Poland 3Horia Hulubei National Institute of Physics and Nuclear Engineering, R-077125 Bucharest, Romania 4CEA, DAM, DIF, F-91297 Arpajon, France 5Institute of Nuclear Research of the Hungarian Academy of Sciences (MTA ATOMKI), H-4001 Debrecen, Hungary (Received 19 June 2015; revised manuscript received 3 August 2015; published 21 August 2015)