Charge Exchange Nuclear Reactions Induced by a Pion

The experimental situation for six types of charge exchange nuclear reactions induced by a pion at a low energy is manifested. Double charge exchange process without any change of the mass, which can never be attained by a nuclear reaction of a single nucleon, is shown to be more abundantly realized by the reaction (rr+, rr-) than (rr-, rr+). The cross section for the reaction (rr+, rr-) turns out to be in the order of several ten!J.b, and the selection rule for the reaction is discussed. Pions have so many different properties from those of nucleons that nuclear reactions by pions may furnish new informations on nuclear structure. It is very favorable that pion brings small momentum at a certain energy owing to its low mass