Spin differences in the Zr90 compound nucleus induced by (p,p') , (p,d) , and (p,t) surrogate reactions

Here, the effect of the production mechanism on the decay of a compound nucleus is investigated. The nucleus ⁹⁰Zr was produced by three different reactions, namely ⁹⁰Zr (p,p') ⁹⁰Zr, ⁹¹Zr (p,d) ⁹⁰Zr, and ⁹²Zr (p,t) ⁹⁰Zr , which served as surrogate reactions for ⁸⁹Zr (n,γ). The spin-parity (J^π) 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 ⁸⁹Zr. Discrete γ rays, associated with transitions in ⁹⁰Zr and ⁸⁹Zr, were measured in coincidence with light ions for scattering angles of 25°–60° and ⁹⁰Zr excitation energies extending above the neutron separation energy. The measured transition systematics were used to gain insights into the J^π distributions of ⁹⁰Zr. The ⁹⁰Zr (p,p') reaction was found to produce fewer γ rays associated with transitions involving high spin states (J = 6–8 ℏ) than the other two reactions, suggesting that inelastic scattering preferentially populates states in ⁹⁰Zr that have lower spins than those populated in the transfer reactions investigated. The γ-ray production was 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.