Pion-nucleus charge-exchange reactions with isobar dynamics

The angular distribution for elastic pion double charge exchange on ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ at 164 MeV is studied. Delta motion and delta-nucleus charge exchange interactions are included and found to be important, but the cross section is not satisfactorily reproduced. Some of our results are consistent with the single datum point for the single charge exchange reaction on ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$.