Let's say a gamma ray shielding material (assume water) has absorbed 1 joule of gamma ray ionizing radiation, does the absorbed 1 joule eventually end up as heat in this material?

I ask this question because I understand that different atoms have different ionization energies and so a photon has to spend this energy in order to ionize the atom. So, does this energy eventually end up as heat in the absorber or is it lost just to eject the electrons from the atoms?

  • $\begingroup$ Yes, free electrons thermalize really fast. Some electrons originating near the surface may be ejected, but man will be turned into heat. $\endgroup$
    – Jon Custer
    Commented Jun 21, 2022 at 1:20
  • $\begingroup$ Do electrons thermalize by attachment to neutral atoms as well? $\endgroup$ Commented Jun 21, 2022 at 6:49

1 Answer 1


Yes. Measuring the heat

X-ray photons have energies that are among the highest for light. When detector material absorbs the energy from an incoming photon, the material heats up just a little. The amount of the temperature difference gives a measure of the energy of the incoming X-ray.

is an excellent way to measure the energy of an ionizing photon. It works for individual soft x-ray photons with energies less than an attojoule.

  • $\begingroup$ I will edit in a copy of the first paragraph for the casual reader , to give you an upvote. You can roll back if you do not like it. $\endgroup$
    – anna v
    Commented Jun 21, 2022 at 4:36

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