Excitation Functions for Helion-Induced Reactions in Iron

Abstract

Target foil stacks of iron were bombarded with beams of helions at incident energies \ensuremath{\le} 70 MeV. $\ensuremath{\gamma}$ spectra of individual foils were measured and analyzed to obtain excitation functions for production of $^{56,\phantom{\rule{0ex}{0ex}}57}\mathrm{Ni}$, $^{55,56,57,58}\mathrm{Co}$, $^{52,54,56}\mathrm{Mn}$, and $^{51}\mathrm{Cr}$; for $^{53}\mathrm{Fe}$ and $^{52}\mathrm{Mn}$, data were obtained for both ground and isomeric states. The yields of $^{56}\mathrm{Co}$ and $^{57}\mathrm{Co}$ are much larger than those of the respective Ni isobars. Recoil measurements (to determine momentum transfer to the target nucleus) were made at ${E}_{h}=41 \mathrm{and} 51$ MeV. These data show $^{57}\mathrm{Co}$ to result principally from direct reactions. There is also evidence of a large contribution by direct reactions to the $^{56}\mathrm{Co}$ yield. The excitation-function data are compared with predictions of compound-nucleus evaporation theory; these indicate compound-nucleus reactions to be the dominant contributor to the yields of $^{51}\mathrm{Cr}$, $^{52,\phantom{\rule{0ex}{0ex}}54}\mathrm{Mn}$, $^{52,\phantom{\rule{0ex}{0ex}}53}\mathrm{Fe}$, $^{55}\mathrm{Co}$, and $^{56,\phantom{\rule{0ex}{0ex}}57}\mathrm{Ni}$.