$g_{9/2}$ neutron strength in the $N=29$ isotones and the $^{52}$Cr($d,p$)$^{53}$Cr reaction

TL;DR

This study investigates the $g_{9/2}$ neutron strength in $^{53}$Cr and neighboring isotones using the $^{52}$Cr$(d,p)$ reaction, revealing that much of the strength is unaccounted for and likely unbound, with theoretical support suggesting the orbit is unbound in $^{53}$Cr.

Contribution

The paper provides new $L$ assignments for states in $^{53}$Cr and suggests the $g_{9/2}$ neutron orbit is unbound, supported by covariant density functional theory calculations.

Findings

Most $g_{9/2}$ strength is near 4 MeV excitation energy.

Observed strength is less than the sum rule predicts.

The $g_{9/2}$ neutron orbit is likely unbound in $^{53}$Cr.

Abstract

We performed a measurement of the $^{52}$Cr$(d,p)^{53}$Cr reaction at 16 MeV using the Florida State University Super-Enge Split-Pole Spectrograph (SE-SPS) and observed 26 states. While all of the states observed here had been seen in previous $(d,p)$ experiments, we changed five $L$ assignments from those reported previously and determined $L$ values for nine states that had not had such assignments made previously. The $g_{9/2}$ neutron strength observed in $^{53}$Cr in the present work and in the $N=29$ isotones $^{49}$Ca, $^{51}$Ti, and $^{55}$Fe via $(d,p)$ reactions is much smaller than the sum rule for this strength. Most of the observed $L=4$ strength in these nuclei is located in states near 4 MeV excitation energy. The remaining $g_{9/2}$ strength may be located in the continuum or may be fragmented among many bound states. A covariant density functional theory calculation provides support for the hypothesis that the $g_{9/2}$ neutron orbit is unbound in $^{53}$Cr. The ($\alpha,^3$He) reaction may provide a more sensitive probe for the missing $g_{9/2}$ neutron strength. In addition, particle-$\gamma$ coincidence experiments may help resolve some remaining questions in this nucleus.