Spin differences in the Zr 90 compound nucleus induced by ( p , p ′ ) , ( p , d ) , and ( p , t ) surrogate reactions

The effect of the production mechanism on the decay of a compound nucleus is investigated. The nucleus Zr-90 was produced by three different reactions, namely Zr-90(p, p') Zr-90, Zr-91(p, d) Zr-90, and Zr-92(p, t) Zr-90, which served as surrogate reactions for Zr-89(n, gamma). The spin-parity (J(pi)) distributions of the states populated by these reactions were studied to investigate the surrogate reaction approach, which aims at indirectly determining cross sections for compound-nuclear reactions involving unstable targets such as Zr-89. Discrete. rays, associated with transitions in Zr-90 and Zr-89, were measured in coincidence with light ions for scattering angles of 25 degrees-60 degrees and Zr-90 excitation energies extending above the neutron separation energy. The measured transition systematics were used to gain insights into the J(pi) distributions of Zr-90. The Zr-90(p, p') reaction was found to produce fewer. rays associated with transitions involving high spin states (J = 6-8 (h) over bar) than the other two reactions, suggesting that inelastic scattering preferentially populates states in Zr-90 that have lower spins than those populated in the transfer reactions investigated. The gamma-ray productionwas also observed to vary by factors of 2-3 with the angle at which the outgoing particle was detected. These findings are relevant to the application of the surrogate reaction approach.