In the two-photon emission process one may use the interference of the two photons to obtain a measure of distance and time scales involved. It will also serve to unravel the different processes contributing on a microscopic scale. In addition to the sequential emission of the two photons there is an alternative process possible where the two photons originate from the decay of a virtual neutral pion. This would provide a unique measure of sub-threshold pion production. The relativistic formalism used in bremsstrahlung will be extended to calculate meson production.
Emphasis lies on the importance of negative energy states and rescattering diagrams.
A position is available for a PhD student on this topic.