Highly Excited Nuclear Residual States in the (γ, , π⁺) Reaction in the Threshold Region

Abstract

Energy distributions of π ⁺ electroproduced on ⁶Li, ⁹Be and ²⁸Si were measured at the electron energy of about 200, MeV. The photon difference method was applied to these (e, , π ⁺) spectra in order to extract the (γ, , π ⁺) cross sections. Present results and previously obtained data show considerable contribution from several discrete levels of the residual nuclei. The spin-isospin flip giant resonance in residual nuclei could be studied up to about 20, MeV residual excitation except in ⁶Li which showed a small quasi-free and/or continuum contribution. In ⁹Be and ²⁸Si, the present results show giant resonances in the residual nuclei with a width of about 15, MeV in the gross shape.