Pickup Behavior inLi6(p, He3)He4andF19(p, α)O16at 18 Mev

Abstract

Differential cross sections were measured for ${\mathrm{F}}^{19}(p, \alpha ){\mathrm{O}}^{16}$, to the ground state, and for ${\mathrm{Li}}^6(p, {\mathrm{He}}^3){\mathrm{He}}^4$. The angular distribution from ${\mathrm{F}}^{19}(p, \alpha ){\mathrm{O}}^{16}$ shows three maxima, which can be fitted approximately by the Born approximation for triton pickup. Empirical adjustment of phase, in the theoretical distribution, gives a better fit with a smaller nuclear radius. The cross section at 18.5 Mev is 1.5 times larger than at 16 Mev. The angular distribution of ${\mathrm{He}}^3$ particles from ${\mathrm{Li}}^6(p, {\mathrm{He}}^3){\mathrm{He}}^4$ shows a maximum at zero degrees, explained qualitatively by deuteron pickup. Cross sections, at 18.5 and 15 Mev, are 1.1 and 1.7 times smaller, respectively, than expected, through pickup theory, from published 14-Mev data on ${\mathrm{Li}}^6(n, t){\mathrm{He}}^4$. Maxima observed at 110 and 180 degrees are examined in terms of direct interaction between the proton and alpha particle in ${\mathrm{Li}}^6$; results are inconclusive, due to inadequacies of current theory. The pickup cross sections give reasonable values of triton and deuteron reduced widths in ${\mathrm{F}}^{19}$ and ${\mathrm{Li}}^6$, respectively.