THE ZR-90(N, P)Y-90 REACTION AT E(N) = 98 MEV

Double-differential cross sections of the Zr-90(n, p) reaction have been measured at 98 MeV in the angular range 0-degrees-30-degrees for excitation energies up to 40 MeV. The spectra have been interpreted in terms of direct and multistep reactions. The contributions from the latter have been calculated using a statistical theory of multistep direct reactions. The direct parts of the spectra have been decomposed into their different multipole components by using peak-fitting and multipole-decomposition techniques, based on sample angular distributions calculated within the distorted-wave Born approximation. An extensive microscopic calculation based on the random-phase approximation has also been performed and the results are compared with the experimental data. A value S(beta)+ = 1.7 +/- 0.2 is extracted for the Gamow-Teller strength, suggesting an occupancy nu-2 = 0.09 +/- 0.01 for the 1g9/2 proton orbital. This value has been compared with recent results from (d, He-3) proton pickup and (e, e'p) knockout reactions.