Pionization experiments in light nuclei

The zero-energy antiproton absorption in light nuclei is considered. The ratios $R_{n/p}$ of antiproton-neutron versus antiproton-proton capture rates in the lightest nuclei $^2$H, $^3$He and $^4$He are analyzed, both from the experimental results and from some selected theoretical models. These models are used as key input in determining the level shifts and widths of the lowest states. We establish the capture orbit in $^3$He to be states of angular momentum $L=2$. Several N-N optical potentials are used to compute the $R_{n/p}$ values for several heavy nuclei and the results are found to be consistent with the data. However, the old chamber experiments studying pionization in Helium, are not consistent with models. Only the Paris potential is likely to succeed provided baryonia states predicted by this model are better understood.