Bromine and iodine excitation-function measurements with protons and deuterons at 3-17 MeV.

Abstract

We report nuclear excitation functions for the reactions [sup 79]Br[([ital p],[ital n])+([ital d],2[ital n])][sup 79]Kr, [sup 81]Br[([ital p],[ital n])+ ([ital d],2[ital n])][sup 81]Br, [sup 81]Br([ital d],[ital p])[sup 82]Br, and [sup 127]I[([ital p],[ital n])+([ital d],2[ital n])][sup 127]Xe. The measurements were made from reaction threshold to 17 MeV with the Lawrence Livermore National Laboratory's Tandem Van de Graaff accelerator using the stacked-foil method. The [sup 79]Br([ital d],2[ital n])[sup 79]Kr and the [sup 81]Br excitation functions are the first reported. The targets consisted of the halides dispersed in the plastic Kapton. The activated targets were assayed using [gamma] counting and mass spectrometry. We found that we had to remeasure the gamma intensities for the [sup 79]Kr decay. The excitation functions were modeled using the Hauser-Feshbach statistical-model code STAPRE, using the exciton preequilibrium model. We found a preference for the back-shifted (BS) level density prescription over the use of the Gilbert-Cameron prescription. For BS, the constant [ital K], governing the transition to equilibrium, was taken as 500 to 700 MeV[sup 3]. These values gave preequilibrium fractions consistent with those we obtained from ion-recoil range studies of light ion reactions. In general the modeling agreed well with experiment. For the deuteron induced reactions, we hadmore » to allow for deuteron breakup using a microscopic breakup fusion approach developed by Udagawa and Tamura. Our analysis of the stripping reaction, [sup 81]Br([ital d],[ital p])[sup 82]Br, by this procedure is especially noteworthy.« less