Study of the Two-Body Force through the (He3,t) Charge-Exchange Reaction onO17andO18

A study of the (${\mathrm{He}}^3$, $t$) reaction on ${\mathrm{O}}^{17}$ and ${\mathrm{O}}^{18}$ has been made at 17.3 MeV, using gas targets of enriched isotopes. The elastic ${\mathrm{He}}^3$ differential cross sections have also been measured and an optical-model analysis performed. The triton angular distributions show the predominance of a direct reaction mechanism. They have been analyzed using a distorted-wave Born-approximation formalism assuming a two-body interaction $V_{0i}$ between the incident and target nucleons; i.e., $V_{0i}={\tau }_0·{\tau }_i(V_{\sigma \tau }{\sigma }_0·{\sigma }_i+V_{\tau })f\left({\mu }_{0i}\right)$. The strengths of the spin-isospin interaction $V_{\sigma \tau }$ and the pure isospin interaction $V_{\tau }$ have been found to be 34.7±6 and 52.0±10 MeV, respectively. The form factors $f\left({\mu }_{0i}\right)$ for both interactions were taken to have a Yukawa shape with a range of 1 F. For the (${\mathrm{He}}^3$, $t$) transitions to the analog state, a further analysis has been made using an exact coupled-channel-equation calculation.