Study of excitation function for alpha induced reactions in natural iridium

Excitation function of (α, χn) reactions on 191Ir (37.3%) and on 191Ir (62.7%) have been measured for 17-55 MeV alpha particle bombarding energy range. Stacked foil activation technique and gamma spectroscopy were used to determine the cross-sections. The experimental data were compared with calculated values obtained by means of geometry dependent hybrid model. The initial exciton number no = 4 with n = 2, p = 2 and h = 0 gives the best agreements with the presently measured values. To calculate the excitation function theoretically the ALICE/LIVERMORE-82 computer code was used. This set of excitation functions provides a data basis for probing the validity of combined equilibrium and pre-equilibrium reaction models in a considerable energy range. (author). 34 refs, 9 figs