Formation of 8He in the 9Be(π–, p)X and 10B(π–, pp)X Stopped Pion Absorption Reactions

Abstract

The structure of levels of the 8He heavy helium isotope has been studied in the 9Be $$({{\pi }^{ - }},p)X$$ and 10B $$({{\pi }^{ - }},pp)X$$ stopped pion absorption reactions. Measurements have been performed with a two-arm multilayer semiconductor spectrometer at the LANL. Indications to the existence of a soft dipole mode at the excitation energy $${{E}_{x}} \approx 3$$ MeV have been obtained. A state with a high excitation energy of 12.2(5) MeV has been observed for the first time.