EXCITATION-FUNCTIONS AND ISOMERIC CROSS-SECTION RATIOS OF THE CU-63(N,ALPHA) CO-60(M,G), CU-65(N,ALPHA) CO-62(M,G), AND NI-60(N,P) CO-60(M,G) PROCESSES FROM 6 TO 15 MEV

Excitation functions were measured for the Cu-63(n,alpha)Co-60m, Cu-65 (n,alpha)Co-62m, and Cu-65(n,alpha)Co-62g reactions over the neutron e nergy range of 6.3 to 14.8 MeV. Use was made of the activation techniq ue in combination with high-resolution gamma-ray spectroscopy. The neu trons were produced via the H-2(d,n)He-3 reaction using a deuterium ga s target at a variable energy compact cyclotron (E(n) = 6.3-11.9 MeV) and via the H-3(d,n)He-4 reaction using a solid Ti-T target at a neutr on generator (E(n) = 13.7-14.8 MeV). From the available experimental d ata isomeric cross section ratios were determined for the isomeric pai r Co-60m,g in Cu-63 Cu(n,alpha) and Ni-60(n,p) reactions, and for the pair Co-62m,g in the Cu-65(n,alpha) reaction. Statistical model calcul ations taking into account precompound effects were performed for the formation of both the isomeric and ground states of the products. The calculational results on the total (n, p) and (n, alpha) cross section s agree well with the experimental data; in the case of isomeric state s, however, some deviations occur. The experimental isomeric cross sec tion ratios are reproduced only approximately by the calculation; at 1 5 MeV the spin distribution of the level density has a significant eff ect on the calculation. For low-lying levels the isomeric cross sectio n ratio depends strongly on the spins of the levels involved and not o n their excitation energies. At a given neutron energy the population of the higher spin isomer appears to be higher in the (n, alpha) proce ss than in the (n, p) reaction.