After fission, what do the fission fragments emit before decaying?

• A. Neutrons and gamma rays
• B. Protons and alpha particles
• C. Only neutrons
• D. Only gamma rays

Answer: (A)

After fission, the two fragments are left in excited nuclear states with excess energy. They shed this energy almost instantly: they emit gamma rays as they de-excite. In addition, a portion of the fragments emit fast (prompt) neutrons during that same immediate aftermath. So the fragments emit both neutrons and gamma rays before any beta decay occurs. Protons and alpha particles aren’t characteristic prompt emissions in this context, and it’s not limited to only one type.