Spectroscopic study of 55Co via the 54Fe(τ, d)55Co and 54Fe(τ, dp̃)54Fe reactions

One-proton and one-neutron knockout reactions from N=Z=28Ni56 to the A=55Spieker1, Gade2, Weißhaar3 et al. 2019Phys. Rev. C13070View full textAdd to dashboardCite

“…Relevant to this work, strong isospin mixing between the T = 3/2, J π = 3/2 − IAS of 55 Cu and a very close-lying T = 1/2, J π = 3/2 − state was observed in a β-decay experiment leading to 55 Ni [42]. Very similar observations had been made in the 1970s for the IAS of 55 Fe in the mirror nucleus 55 Co [28,29,43]. The recent β-decay data on 55 Ni hint at slightly stronger isospin mixing in 55 Co [42] as compared to the earlier work mentioned above.…”

“…Therefore, spectroscopic factors C 2 S for the one proton transfer from 54 Fe (ground state) to 55 Co (J π = 3/2 − i ) were also calculated and compared to the data from Table 1 of [29]. To obtain agreement between the shell-model spectroscopic factors and the experimentally determined ratio of C 2 S(3/2 − 1 )/C 2 S(3/2 − 2 ) = 1.54 (22) in 55 Co, derived as the average from several 54 Fe to 55 Co transfer reactions [29], mixing amplitudes of α = 0.995 +0.003 −0.004 (α 2 = 0.990 +0.005 −0.010 ) and β =−0.10 +0.04 −0.03 (β 2 = 0.010 +0.010 −0.005 ) result in a model with two unperturbed 3/2 − j ( j = I, II) states. The wave functions of the mixed states are then given by…”

“…In terms of single-particle properties, a number of experiments [27][28][29][30][31][32][33][34][35][36] and theoretical studies [16,17,[19][20][21]37,38] have been performed to identify the fragments of the singleparticle levels relative to the N = Z = 28 core and have also suggested the existence of 2 + 1 ( 56,58 Ni) ⊗ 1 f −1 7/2 core-coupled excitations with J π = 3/2 − ,...,11/2 − in the vicinity of 56 Ni [39][40][41]. Only recently, an inverse-kinematics one-neutron transfer experiment 1 H( 56 Ni, d ) 55 Ni populated for the first time single-hole-like states directly from the 56 Ni ground state [36], however, without detecting subsequent γ -ray emission.…”

Inelastic proton amplitudes forf-wave resonances in55Co

“…For inelastic scattering from f-wave resonances, l'= I, 3 and 5 are allowed. Although, again, the l'= 3 penetrability is only about 2 ~o of the l'= 1 value, Fortier et al, in a S4Fe(3He, dp) experiment [6], observed an /'=3 admixture of more than 20 ~o for the f-wave analogue in question. In the present analysis, both l'= 1 and /'=3 contributions have been included.…”

“…The sensitivity of these measurements to small admixtures of higher 1' values is demonstrated for an fs/2 analogue in 5SCo. This analogue, which had been investigated with high resolution at this laboratory [5], was chosen for study in part because measurements * Supported in part by US Department of Energy [6] with the (3He, dp) reaction indicated a preferred solution with 23 % of the total inelastic width in the l' = 3 channel. Resonances studied in the present work included the five fragments of the f-wave analogue at Ep=3.80MeV, as well as five other f-wave resonances well removed from the analogue.…”