The existence of the ${}^7\mathrm{H}$ nuclear system was investigated via a one-proton transfer reaction with a ${}^8\mathrm{He}$ beam at $15.4\mathrm{A}\mathrm{MeV}$ and a ${}^{12}\mathrm{C}$ gas target. The experimental setup was based on the active-target MAYA which allowed a complete reconstruction of the reaction kinematics. The existence of the ${}^7\mathrm{H}$ was confirmed with the identification of seven events where the system was formed with a resonance energy of ${0.57}_{-0.21}^{+0.42}\mathrm{MeV}$ above the ${}^3\mathrm{H}+4n$ threshold and a resonance width of ${0.09}_{-0.06}^{+0.94}\mathrm{MeV}$. This study represents an unambiguous proof of the existence of the most neutron-proton unbalanced system presently found.

• Received 8 February 2007

DOI:https://doi.org/10.1103/PhysRevLett.99.062502