Formation of the Heavy Isotope $${}^{\boldsymbol{6}}$$He upon Stopped Pion Absorption by Nuclei

A survey of experimental results on the level structure in the heavy helium isotope $${}^{6}$$ He that were obtained in reactions induced by stopped pion absorption in $${}^{9}$$ Be, $${}^{10,11}$$ B, and $${}^{12}$$ C light nuclei is presented. The respective measurements were performed on the low-energy pion channel of the accelerator at the Los Alamos National Laboratory (LANL) by means of a two-arm semiconductor spectrometer. A high statistical significance of the results was attained over a broad excitation-energy range extending up to 40 MeV. Several highly excited states, including $$t+t$$ cluster resonances, were revealed for the first time.