EXCITATION-FUNCTIONS OF SOME NEUTRON THRESHOLD REACTIONS ON Y-89 IN THE ENERGY-RANGE OF 7.8 TO 14.7 MEV

Excitation functions were measured for Y-89(n,2n)Y-88, Y-89(n,p)Sr-89 and Y-89(n,alpha)Rb-86 reactions from their respective thresholds up t o 14.7 MeV using the activation technique. Quasi-monoenergetic neutron s in the energy range of 7.8 to 13.3 MeV were produced via the H-2(d,n )He-3 reaction on a D-2 gas target at the Julich compact cyclotron (CV 28), and monoenergetic neutrons in the range of 13.8 to 14.7 MeV usin g the D-T neutron generator at Debrecen. For characterization of Y-88 and Rb-86, high-resolution gamma-ray spectrometry was applied. The lat ter product was also separated radiochemically and characterized by lo w-level beta(-) counting; the results obtained using the two counting methods were generally in good agreement. The product Sr-89 is a pure beta(-) emitter: its activity was exclusively assayed via radiochemica l separation and beta(-) counting. Our results agree with the literatu re values on the (n,2n) reaction and provide the first consistent set of data on the (n,p) and (n,alpha) reactions near their thresholds. St atistical model calculations incorporating precompound effects were pe rformed on the three excitation functions under consideration. The exp erimental and theoretical results were found to be in good agreement. Some systematic trends in the excitation functions in this mass region are discussed.