Complex sentence: In some instances, however, predictions based on this model underestimate the total amount of energy released in the form of gamma rays, ie. nuclei appeare to have more than enough energy to eject neutrons, but decayed by gamma ray emission instead.
Split into simpler sentences: In some instances, however, predictions based on this assumption underestimated the total amount of energy released in the form of gamma rays. The nuclei appeared to have more than enough energy to eject neutrons, but they were decaying by gamma ray emission instead.