(p, n) Reaction on Zr 91 Followed by Proton Emission

The reaction Zr91 (p,n) Nb91, where Nb91 denotes the isobaric analogue of the ground state of Zr91, was investigated by observing the proton decay of Nb91. Proton spectra corresponding to 13.0, 13.15, and 13.3 MeV incident proton energies were recorded. The three spectra were then added in order to accentuate any proton group with energy largely independent of the incident proton energy. This procedure broadened extensively all proton peaks with the exception of one. It is strongly suggested that this peak results from the proton decay of Nb91 to the ground state of Zr90. The observed energy release in this decay was 4.70 plus or minus 0.10 MeV. The Coulomb displacement energy is therefore 11.90 plus or minus 0.10 MeV. The observed integrated cross section for the Zr91 (p,n) Nb91 reaction, assuming isotropic decay for Nb91, was approximately 5 mb. As expected, no such effect was observed when Zr90 was used as a target. (Author)