ISOMERIC CROSS-SECTION RATIOS FOR THE FORMATION OF GE-75(M,G) IN (N,P), (N,ALPHA), AND (N,2N) REACTIONS FROM 6 TO 15 MEV

The isomeric cross-section ratio sigma(m)/(sigma(m), + sigma(g)) for the formation of Ge-75(m,g) was measured in As-75(n,p), Se-78(n,alpha), and Ge-76(n,2n) processes in the neutron energy range of 6.3 to 14.7 MeV. Use was made of the activation technique in combination with high-resolution gamma-ray spectrometry. The ratio is relatively high (>0.70) even at low incident particle energies and appears to increase only slightly with increasing energy. Statistical model calculations, taking into account precompound effects, were performed for the total reaction channel as well as for the isomer ratio. In either case, good agreement was obtained. For the investigated isomeric pair, no significant effect of reaction channels on the isomeric cross-section ratio was observed.