We propose to study diffractive phenomena caused by 100 BeV pions, using a new technique, which consists in associating with the high energy interaction, the detection of photons resulting from the de-excitation of nuclear levels. Knowledge of the quantum numbers both for the ground state and the nuclear levels of the nuclei used, adds information as to the type of interaction. In particular, the use of the 4.4 MeV level of Carbon guarantees that the exchange quantum has isotopic spin 0. In addition, evidence resulting from our tests at Berkeley seems to further encourage the notion that this level selects to a good extent phenomena of the diffractive type. We ask for 150 hours of running on a 100 BeV/c pion beam.