New Isotope of Helium:He7

Abstract

Energy spectra have been measured at 15 scattering angles for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ ions arising from the triton bombardment of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$. A peak which appeared in the spectra at all scattering angles is attributed to the ground state of ${}_{}{}^7{}_{}{}^{}\mathrm{He}$. The $Q$ value of the reaction ${}_{}{}^7{}_{}{}^{}\mathrm{Li}(t, {}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^7{}_{}{}^{}\mathrm{He}$ corresponds to ${}_{}{}^7{}_{}{}^{}\mathrm{He}$ being unbound to neutron decay by 0.42±0.06 MeV. The width of the state was determined to be 0.17±0.04 MeV.