In a photoelectric absorption event, which additional photon is emitted along with the ejected electron?

• A. Bremsstrahlung photon
• B. Characteristic photon
• C. Scattered photon
• D. No photon

Answer: (B)

When a photon is absorbed by an atom and ejects an inner-shell electron, the atom is left with a vacancy. The remaining electrons drop to fill that vacancy, and the energy released in this relaxation is emitted as a photon with a discrete energy specific to the element—this is a characteristic X-ray. That is why the correct choice is the characteristic photon: it directly results from the atom’s de-excitation after inner-shell ionization. Bremsstrahlung would come from deceleration of a charged particle, not from this de-excitation process; a scattered photon would indicate the photon has undergone scattering (like Compton scattering), not the atom’s relaxation; and although some relaxations can happen via Auger emission without a photon, when a photon is emitted, it is the characteristic one.