  We report the first experimental observation of the pionic fusion of two
heavy ions. The 12C(12C,24Mg)pi0 and 12C(12C,24Na)pi+ cross sections have been
measured to be 208 +/- 38 and 182 +/- 84 picobarns, respectively, at E_cm = 137
MeV. This cross section for heavy-ion pion production, at an energy just 6 MeV
above the absolute energy-conservation limit, constrains possible production
mechanisms to incorporate the kinetic energy of the entire projectile-target
system as well as the binding energy gained in fusion.
