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Register a new userNeutron spectroscopic factors of $^{55}$Ni hole-states from (p,d) transfer reactions
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Spectroscopic information has been extracted on the hole-states of $^{55}$Ni, the least known of the quartet of nuclei ($^{55}$Ni, $^{57}$Ni, $^{55}$Co and $^{57}$Co), one neutron away from $^{56}$Ni, the N=Z=28 double magic nucleus. Using the $^{1}$H($^{56}$Ni,d)$^{55}$Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f$_{7/2}$, p$_{3/2}$ and the s$_{1/2}$ hole-states of $^{55}$Ni. This new data provides a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s$_{1/2}$ hole-state below Fermi energy.
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We present a high-resolution in-beam $gamma$-ray spectroscopy study of excited states in the mirror nuclei $^{55}$Co and $^{55}$Ni following one-nucleon knockout from a projectile beam of $^{56}$Ni. The newly determined partial cross sections and the $gamma$-decay properties of excited states provide a test of state-of-the-art nuclear structure models and probe mirror symmetry in unique ways. A mirror asymmetry for the partial cross sections leading to the two lowest $3/2^-$ states in the $A = 55$ mirror pair was identified as well as a significant difference in the $E1$ decays from the $1/2^+_1$ state to the same two $3/2^-$ states. The mirror asymmetry in the partial cross sections cannot be reconciled with the present shell-model picture or small mixing introduced in a two-state model. The observed mirror asymmetry in the $E1$ decay pattern, however, points at stronger mixing between the two lowest $3/2^-$ states in $^{55}$Co than in its mirror $^{55}$Ni.
To improve the effective interactions in the pf shell, it is important to measure the single particle- and hole- states near the N=28 shell gap. In this paper, the neutron spectroscopic factors of hole-states from the unstable neutron-rich 45Ar (Z=18, N=27) nucleus have been studied using 1H(46Ar, 2H)45Ar transfer reaction in inverse kinematics. Comparison of our results with the particle-states of 45Ar produced in 2H(44Ar, H)45Ar reaction shows that the two reactions populate states with different angular momentum. Using the angular distributions, we are able to confirm the spin assignments of four low-lying states of 45Ar. These are the ground state (f7/2), the first-excited (p3/2), the s1/2 and the d3/2 states. While large basis shell model predictions describe spectroscopic properties of the ground and p3/2 states very well, they fail to describe the s1/2 and d3/2 hole-states.
Existing measurements of the angular distributions of the ground-state to ground-state transitions of the 12C(d,p)13C and 13C(p,d)12C neutron-transfer reactions have been analyzed systematically using the Johnson-Soper adiabatic and distorted-wave theories. When using a consistent set of physical inputs the deduced spectroscopic factors are consistent to within 20% for incident deuteron energies from 6 to 60 MeV. By contrast, original analyses of many of these data quoted spectroscopic factors that differed by up to a factor of five. The present analysis provides an important reference point from which to assess the requirements of future spectroscopic analyses of transfer reactions measured in inverse kinematics using rare nuclei.
An overall reduction factor (ORF) is introduced for studying the quenching of single particle strengths through nucleon transfer reactions. The ORF includes contributions of all the probed bound states of the residual nucleus in a transfer reaction and permits a proper comparison with results of inclusive knockout reactions. A systematic analysis is made with 103 sets of angular distribution data of $(p,d)$ reactions on 21 even-even targets with atomic mass numbers from 8 to 56 using the consistent three-body model reaction methodology proposed in [J. Lee, J.A. Tostevin, B.A. Brown, et al., Phys. Rev. C 73, 044608 (2006)]. The extracted ORFs are found to be nearly independent on the nuclear isospin asymmetry, which is different from the systematics of inclusive knockout reactions but is consistent with the recent measurement of $(d,t)$, $(d,3He)$, $(p,2p)$, and $(p,pn)$ reactions on nitrogen and oxygen isotopes and textit{ab initio} calculations.
An improved description of single neutron stripping from $^{34,36,46}$Ar beams at 33 MeV/nucleon by a hydrogen target is presented and the dependence on the neutron-proton asymmetry of the spectroscopic factors is further investigated. A finite range adiabatic model is used in the analysis and compared to previous zero range and local energy approximations. Full three-body Faddeev calculations are performed to estimate the error in the reaction theory. In addition, errors from the optical potentials are also evaluated. From our new spectroscopic factors extracted from transfer, it is possible to corroborate the neutron-proton asymmetry dependence reported from knockout measurements.
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