Isomeric Character of the Lowest Observed 4+ State in S 44

Author(s): Parker, JJ; Wiedenhover, I; Cottle, PD; Baker, J; McPherson, D; Riley, MA; Santiago-Gonzalez, D; Volya, A; Bader, VM; Baugher, T; Bazin, D; Gade, A; Ginter, T; Iwasaki, H; Loelius, C; Morse, C; Recchia, F; Smalley, D; Stroberg, SR; Whitmore, K; Weisshaar, D; Lemasson, A; Crawford, HL; Macchiavelli, AO; Wimmer, K | Abstract: © 2017 American Physical Society. Previous experiments observed a 4+ state in the N=28 nucleus S44 and suggested that this state may exhibit a hindered E2-decay rate, inconsistent with being a member of the collective ground state band. We populate this state via two-proton knockout from a beam of exotic Ar46 projectiles and measure its lifetime using the recoil distance method with the GRETINA γ-ray spectrometer. The result, 76(14)stat(20)syst ps, implies a hindered transition of B(E2;4+→21+)=0.61(19) single-particle or Weisskopf units strength and supports the interpretation of the 4+ state as a K=4 isomer, the first example of a high-K isomer in a nucleus of such low mass.