Rossi's stay in Manchester was brief, but productive. At this time, a clear understanding of the soft component was available. In 1934, Hans Bethe and Walter Heitler published a quantitative description not only of the production of electron-positron pairs by energetic photons, but also of the production of photons by energetic electrons and positrons. At Manchester, Rossi collaborated with Ludwig Jánossy on an experiment which demonstrated the correctness of the Bethe-Heitler theory of the second process, which had not yet been fully confirmed. This experiment also introduced the technique of anti-coincidence, which has become a ubiquitous feature of instruments for detecting and analyzing energetic particles.