Analog (p,n) cross sections of the zirconium isotopes at 18 and 25 MeV

The differential cross sections for the (p,n) reaction to the ground-state analogs of the lightest four stable zirconium isotopes (90, 91, 92, and 94) have been measured at proton energies of 18 and 25 MeV. Integrated cross sections are found to deviate from the expected linear dependence on neutron excess as was previously found for the molybdenum isotopes. The observed dependence is in quantitative agreement with calculations, including inelastic couplings used to explain the molybdenum results. The energy dependence of the zirconium analog cross sections confirms the resonant-type enhancement of the low energy (p,n) excitation function observed previously for the molybdenum isotopes