Use of the (e,e'n) reaction to study the giant multipole resonances in 116Sn.

Abstract

The giant multipole resonances in $^{116}\mathrm{Sn}$ have been studied using the (e,e'n) reaction. Data were taken at effective momentum transfers of 0.37, 0.45, and 0.55 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$ and a multipole analysis of the data was performed. The inferred multipole strength functions identify the E2 and E0 resonances as distinct peaks at 12.2 and 17.9 MeV, respectively. The energy-weighted sum-rule strengths for the E2 and E0 resonances, obtained using a Lorentzian fit to the data, are 34\ifmmode\pm\else\textpm\fi{}13% and 93\ifmmode\pm\else\textpm\fi{}37%. When compared with results from alpha scattering and pion scattering the sum-rule strengths exhibit approximate agreement, but the E0 strength identified in this measurement lies at higher excitation energy, consistent with the trend observed in heavier nuclei. The (e,e'n) data are compared with a continuum random phase approximation (RPA) calculation of the E2 and E0 strengths, and with an open-shell RPA calculation of the E2 strength. Both calculations disagree with the data in the region of the E2 resonance.