Pionic probes for exotic nuclei

These new tools are reactions involving pions in the incident and/or outgoing channels can be used in the study of exotic nuclei far from the valley of stability. The most useful of these reactions are the pion double charge exchange reactions, both ( pi /sup +/, pi /sup -/) and ( pi /sup -/, pi /sup +/). The ( pi /sup -/ pi /sup +/) reaction has been successfully used to study T/sub Z/=3 nuclei such as /sup 18 /C and /sup 26/Ne, and the pi /sup +/, pi /sup -/ reaction has been used to study T/sub Z/=-2 nuclei such as /sup 12/O, /sup 16/Ne, /sup 24/Si and /sup 32/Ar, and T/sub Z/=-1 nuclei such as /sup 58/Zn. Perhaps the most exciting aspect of these reactions lies in the fact that they can be used to study excited states of exotic nuclei and nuclei which are significantly unbound. An example of the latter is provided by the recent identification and mass measurement of /sup 9 /He. Even more exotic systems such as /sup 7/H and /sup 5/H, which are of great astrophysical interest, are the subjects of current investigations. Recently the ( pi /sup -/, rho ) reaction has been used to identify and study /sup 8/He and /sup 5/H. (39 refs).