Inclusive measurement of (p,-xn) double charge exchange reactions on bismuth from threshold to 800 MeV

M. Dombsky*, J. M. Dauria, I. Kelson, A. I. Yavin, T. E. Ward, J. L. Clark, T. Ruth, G. Sheffer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The energy dependence of the total angle-integrated cross section for the production of astatine isotopes from (p,-xn) double charge exchange reactions on bismuth (209Bi) was measured from 120 to 800 MeV using activation and radiochemical techniques. Chemical yields were estimated by direct radioassaying of At211 activity in thin (1 mg/cm2), irradiated bismuth targets. Calculations of the contributions of secondary (two-step) reactions to these measured astatine yields were performed, based partially upon the observed At211 activity although even at the highest energies, the contribution to products lighter than At207 was negligible. These data for products with as many as seven neutrons removed from the doubly coherent product (210At) display nearly Gaussian shapes for the mass distributions of the astatine residues, with the maximum occurring for about At204. The most probable momentum transfer deduced from these distributions for the initial - production step was 335 MeV/c. The observed excitation functions display a behavior similar to that observed for the yield of Po210 from a (p,0) reaction on Bi209, but radically different from that observed for inclusive - reactions on a heavy nucleus. These data are discussed in terms of recent theoretical approaches to negative pion production from bismuth. In addition, a simple, schematic model is developed to treat the rapidly decreasing percentage of the total inclusive - emission which is observed for this double charge exchange reaction. This model reflects the opacity of a nucleus to a source of internal energetic protons.

Original languageEnglish
Pages (from-to)253-263
Number of pages11
JournalPhysical Review C - Nuclear Physics
Issue number1
StatePublished - 1985


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