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

Abstract

The structure of levels of the $^{8}$He heavy helium isotope has been studied in the $^{9}$Be$({{\pi }^{ - }},p)X$ and $^{10}$B$({{\pi }^{ - }},pp)X$ 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