Particle- γ coincidence spectroscopy of the N = 90 nucleus 154Gd by (p, tγ)

Author(s): Allmond, JM; Beausang, CW; Ross, TJ; Humby, P; Basunia, MS; Bernstein, LA; Bleuel, DL; Brooks, W; Brown, N; Burke, JT; Darakchieva, BK; Dudziak, KR; Evans, KE; Fallon, P; Jeppesen, HB; LeBlanc, JD; Lesher, SR; McMahan, MA; Meyer, DA; Phair, L; Rasmussen, JO; Scielzo, ND; Stroberg, SR; Wiedeking, M | Abstract: © 2017, SIF, Springer-Verlag Berlin Heidelberg. A segmented Si-telescope and HPGe array, STARS-LIBERACE, was used to study the 156Gd(p, tγ)154Gd direct reaction by particle- γ coincidence spectroscopy. New cross sections with a 25MeV proton beam are reported and compared to previous (p,t) and (t,p) studies. Furthermore, additional evidence for coexisting Kπ=01+,21+ and 02+, 22+ configurations at N = 90 is presented. Direct and indirect population patterns of the low-lying states are also explored. Review of the new and existing evidence favors an interpretation based on a configuration-dependent pairing interaction. The weakening of monopole pairing strength and an increase in quadrupole pairing strength could bring 2p-2h 0 + states below 2 Δ. This may account for a large number of the low-lying 0 + states observed in two-nucleon transfer reactions. A hypothesis for the origin of the 02+ and 03+ states is provided.