Background: The low-lying level structure of ${}^{13}\mathrm{Be}$ is still not fully understood; specifically, it has not been ruled out that the first $1/2^{-}$ state could be located above the isomeric $0_2^{+}$ state of ${}^{12}\mathrm{Be}$ and decay via that state.

Purpose: Search for a possible decay path of ${}^{13}\mathrm{Be}$ excited states through the isomeric $0_2^{+}$ state in ${}^{12}\mathrm{Be}$.

Method: The invariant mass technique was used to reconstruct (${}^{12}\mathrm{Be} +$ n) decay energies from neutron removal reactions of ${}^{14}\mathrm{Be}$ at 78 MeV/u on a ${}^9\mathrm{Be}$ target in coincidence with delayed $\gamma$ rays. Charged particles and neutrons were detected and identified with a telescope and a subset of the Modular Neutron Array (MoNA), respectively, around zero degrees. The CAESium-iodide scintillator ARray (CAESAR) was located around the telescope measuring the $\gamma$ rays.

Results: No evidence for the population and decay of the $0_2^{+}$ state in ${}^{12}\mathrm{Be}$ was observed. From the nonobservation of 511 keV $\gamma$ rays an upper limit of 6% of the $p$-wave contribution was extracted.

Conclusions: The previously observed $p$-wave resonance at about 500 keV does not decay via the isomeric state and thus corresponds to the ground state of ${}^{13}\mathrm{Be}$ decaying to the ${}^{12}\mathrm{Be}$ ground state.

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• Energy levels
• Isomer decays
• Nuclear structure & decays
• 6 ≤ A ≤ 19