Spectroscopic factors of neutron-hole and proton-hole states in ${}^{131}\mathrm{Sn}$ and ${}^{131}\mathrm{In}$, respectively, were measured using one-nucleon removal reactions from doubly magic ${}^{132}\mathrm{Sn}$ at relativistic energies. For ${}^{131}\mathrm{In}$, a 2910(50)-keV $\gamma$ ray was observed for the first time and tentatively assigned to a decay from a ${5/2}^{-}$ state at 3275(50) keV to the known ${1/2}^{-}$ level at 365 keV. The spectroscopic factors determined for this new excited state and three other single-hole states provide first evidence for a strong fragmentation of single-hole strength in ${}^{131}\mathrm{Sn}$ and ${}^{131}\mathrm{In}$. The experimental results are compared to theoretical calculations based on the relativistic particle-vibration coupling model and to experimental information for single-hole states in the stable doubly magic nucleus ${}^{208}\mathrm{Pb}$.

• Received 20 September 2019
• Revised 29 November 2019

DOI:https://doi.org/10.1103/PhysRevLett.124.022501