Energy dependence of stretched states excited in (p,n) reactions

We studied the energy dependence of the excitation of the ‘‘1ħω,’’ ${\mathit{J}}^{\mathrm{\pi }}$=$6^{\mathrm{-}}$, state in the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$(p,n${)}^{28}$P(4.95 MeV) reaction and the ‘‘0ħω,’’ ${\mathit{J}}^{\mathrm{\pi }}$=$9^{+}$, state in the ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$(p,n${)}^{88}$Y(1.48 MeV) reaction at ${\mathit{E}}_{\mathit{p}}$=100, 200, 300, and 400 MeV. Differential cross sections for these reactions were measured and compared to distorted-wave impulse-approximation (DWIA) calculations. The ratio of the ${}_{}{}^{88}{}_{}{}^{}\mathrm{Sr}$ to the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ DWIA normalizations is independent of beam energy, indicating that the systematic difference in DWIA normalizations reported earlier between 0ħω and 1ħω stretched states is a nuclear-structure effect. Additionally the DWIA normalization for each reaction is independent of the beam energy indicating that the necessary ingredients for DWIA calculations to describe these transitions consistently are well understood.