Stability of bound states of negative pions and neutrons

The problem of stable bound states of a system composed of N neutrons and Z negative pions is discussed. Calculations performed within a theoretical model indicate that one needs at least 5 pions and around 8 neutrons in order to get binding. The stability of the system against either pion or neutron emission is investigated, as well as the stability against its possible weak decay modes. Results for several values of N and Z are presented.