${}^{54}$Fe($d$,$p$)${}^{55}$Fe and the evolution of single neutron energies in the $N=29$ isotones

Abstract

A measurement of the ${}^{54}$Fe($d$,$p$)${}^{55}$Fe reaction at 16 MeV was performed using the Florida State University Super-Enge Split-Pole Spectrograph to determine single-neutron energies for the $2p_{3/2}$, $2p_{1/2}$, $1f_{5/2}$, $1g_{9/2}$ and $2d_{5/2}$ orbits. Two states were observed that had not been observed in previous (d, p) measurements. In addition, we made angular momentum transfer, \textit{L}, assignments to four states and changed \textit{L} assignments from previous ($d$, $p$) measurements for nine more states. The spin-orbit splitting between the $2p_{3/2}$ and $2p_{1/2}$ orbits is similar to that in the other $N=29$ isotones and not close to zero as a previous measurement suggested. While the $1f_{5/2}$ single neutron energy is significantly lower in ${}^{55}$Fe than in ${}^{51}$Ti, as predicted by a covariant density functional theory calculation, the single-neutron energy for this orbit in ${}^{55}$Fe is more than 1 MeV higher than the calculation suggests, although it is only 400 keV above the $2p_{1/2}$ orbit. The summed spectroscopic strength we observed for the $1g_{9/2}$ orbit up to the single-neutron separation energy of 9.3 MeV is only 0.3. This is surprising because the $1g_{9/2}$ orbit is predicted by Togashi \textit{et al.} to be located only 5.5 MeV above the $2p_{3/2}$ orbit.

16 pages, 6 figures. arXiv admin note: text overlap with arXiv:2106.05781

References in corpus (4)

• Building relativistic mean field models for finite nuclei and neutron stars
• Large-scale shell-model calculations for unnatural-parity high-spin states in neutron-rich Cr and Fe isotopes
• ${}^{50}$Ti($d$,$p$)${}^{51}$Ti, single neutron energies in the $N=29$ isotones and the $N=32$ subshell closure
• Role of cross-shell excitations in the reaction 54Fe(d_pol,p)55Fe

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• The CeBrA demonstrator for particle-$\gamma$ coincidence experiments at the FSU Super-Enge Split-Pole Spectrograph
• Nuclear structure and direct reaction studies in particle-$\gamma$ coincidence experiments at the FSU John D. Fox Superconducting Linear Accelerator Laboratory
• $g_{9/2}$ neutron strength in the $N=29$ isotones and the ${}^{52}$Cr($d,p$)${}^{53}$Cr reaction
• Experimental study of ${}^{53}$Cr via the $(d,p\gamma )$ reaction