학술논문
Unexpected distribution of $ u1f_{7/2}$ strength in the calcium isotopes at $N$=30
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article
Author
Crawford, HL; Macchiavelli, AO; Fallon, P; Albers, M; Bader, VM; Bazin, D; Campbell, CM; Clark, RM; Cromaz, M; Dilling, J; Gade, A; Gallant, AT; Holt, JD; Janssens, RVF; Krücken, R; Langer, C; Lauritsen, T; Lee, IY; Menéndez, J; Noji, S; Paschalis, S; Recchia, F; Rissanen, J; Schwenk, A; Scott, M; Simonis, J; Stroberg, SR; Tostevin, JA; Walz, C; Weisshaar, D; Wiens, A; Wimmer, K; Zhu, S
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Abstract
The calcium isotopes have emerged as an important testing ground for newmicroscopically derived shell-model interactions, and a great deal of focus hasbeen directed toward this region. We investigate the relative spectroscopicstrengths associated with $1f_{7/2}$ neutron hole states in $^{47, 49}$Cafollowing one-neutron knockout reactions from $^{48,50}$Ca. The observedreduction of strength populating the lowest 7/2$^{-}_{1}$ state in $^{49}$Ca,as compared to $^{47}$Ca, is consistent with the description given byshell-model calculations based on two- and three-nucleon forces in the neutron$pf$ model space, implying a fragmentation of the $l$=3 strength tohigher-lying states. The experimental result is inconsistent with both theGXPF1 interaction routinely used in this region of the nuclear chart and withmicroscopic calculations in an extended model space including the $u1g_{9/2}$orbital.