Observation of the Nuclear Isovector Monopole Resonance

Abstract

Observation of the $T+1$ component of the isovector monopole and the giant dipole resonances in the reactions $^{90}\mathrm{Zr}$ and $^{120}\mathrm{Sn}({\ensuremath{\pi}}^{\ensuremath{-}}, {\ensuremath{\pi}}^{0})$ at ${T}_{{\ensuremath{\pi}}^{\ensuremath{-}}}=165$ MeV is reported. The isobaric analog state and $T\ensuremath{-}1$ component of the giant dipole resonance in the reaction $^{120}\mathrm{Sn}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{0})$ were also observed. Excitation energies and widths of the monopole are given.