AVERAGE ANGULAR-MOMENTUM IN COMPOUND NUCLEUS REACTIONS DEDUCED FROM ISOMER RATIO MEASUREMENTS

We have measured the ratio of the yields for the metastable and ground states of Te-119 produced in the fusion-evaporation reactions Pd-110( C-12,3n) and In-115(Li-7,3n) by off-line observation of delayed gamma- ray emission. The absolute cross sections for the formation of the met astable (J(pi) = 11/2(-), Tin = 4.68 d) and ground (J(pi) = 1/2(+), T- 1/2 = 16.05 h) states were determined at energies close to the Coulomb barrier for both systems. We have deduced the average angular momentu m from these isomer ratio measurements through statistical model calcu lations. The deduced mean angular momentum agrees quite well with thos e calculated by a simple fusion model. The expected constant value of thr average total angular momentum at subbarrier energies was confirme d for the C-12+ Pd-110 system. The predicted variation of the mean orb ital angular momentum with the reduced mass of the entrance channel wa s also verified.