# Answer to Question #308 in Quantum Mechanics for Luene

Question #308

Show that the γ-quantum can not form a pair outside the nucleus field, even if such process is energetically possible.

Expert's answer

To form pair it is necessary that the γ-quantum energy is greater than 2mc², where m is the mass of each particle. Obviously, you can always go to a reference system where the γ-quantum energy is less than 2mc² and the pair creation would be impossible. But if this process is not possible in one reference system, it is not possible in any other.

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