Modeling Pionic Fusion
  Recently observed rare heavy ion fusion processes, where the entire available energy is carried away by a single pion, is an example of extreme collectivity in nuclear reactions. We calculate the cross section in the approximation of sudden overlap, modeling the initial and final nuclei by moving harmonic oscillator potentials. This allows for a fully quantum-mechanical treatment, exact conservation of linear and angular momenta and fulfillment of the Pauli principle. The results are in satisfactory agreement with data. Mass number dependence and general trends of the process are discussed. 
Alexander Volya, Scott Pratt and Vladimir Zelevinsky