EXCITATION-FUNCTIONS OF THE Y-89(N,N'GAMMA)Y-89(M) AND Y-89(N,ALPHA-GAMMA)RB-86(M) PROCESSES

Excitation functions of the Y-89(n,n' gamma)Y-89(m) and Y-89(n,alpha g amma)Rb-86(m) reactions were measured over the neutron energy range of 6.2 to 14.7 MeV, using the activation technique in combination with o ff-line gamma-ray spectrometry. Neutrons in the energy range of 6 to 1 2.4 MeV were produced using the H-2(d,n)He-3 reaction on a D-2 gas tar get and in the region of 14 MeV at a D-T generator. The half-life of Y -89(m) was redetermined and found to be 15.28+/-0.17 s, i.e., slightly shorter than the literature value of 16.09 s. Statistical model calcu lations taking into account precompound effects were performed for the strong Y-89(n,n' gamma)Y-89(m) channel as well as for the weak Y-89(n ,alpha gamma)Rb-86(m) process. The experimental data for both the reac tions are well described by the calculation over the whole investigate d energy range. For the Y-89(n,alpha gamma)Rb-86(m,g) process, the iso meric cross section ratio [sigma(m)/(sigma(m) + sigma(g))] was deduced . A comparison with the results of nuclear model calculations showed g ood agreement. [S0556-2813(98)05210-8].