# Photon emission during x-Ray ionization process

1. Aug 20, 2014

### mark_usc

Dear mates:

During ionization with radiant energy there is a photon emission (see http://hyperphysics.phy-astr.gsu.edu/hbase/mod3.html). I know photon emission occurs by a decay of radiant energy from a excited state and what is confusing to me (I can't find a logical conection) is that the expulsed electron from ionization takes all the radiant energy and leaves the atom with out excited levels for energy decayment.

Marco Uscanga

Last edited: Aug 20, 2014
2. Aug 20, 2014

### euquila

I'm not sure what you find confusing. An x-ray is colliding with an atom and -- because it has so much energy compared to the electric potential energy that holds the electron to the nucleus -- it knocks off the electron (ionizes it). Quantum mechanics tells you that there is also a probability that a photon is emitted as a result of this collision, which would carry off some of the momentum/energy. If you repeat the experiment over and over, some of the time you will get no photon, and sometimes you will get a photon...
You don't necessarily have to have excited bound electrons in order to create a photon... I don't know where you got this notion. Photon(s) can result from a particle collision directly (like a meson hitting a proton for example).

3. Aug 20, 2014

### mark_usc

ok Euquila!! I think I have to take into account that Quantum mechanics tells you that there is also a probability that a photon is emitted as a result of this collision, which would carry off some of the momentum/energy

4. Aug 20, 2014

### euquila

Ya quantum mechanics is very interesting. For example, it is also possible that in this collision that a electron-positron pair is created, provided that the x-ray has enough energy with respect to the sum of the rest masses of these 2 daughter particles E_photon >= 2*m_e, with c=1. What you should realize is that when 2 particles collide, there are many outcomes that can occur with various (or even equal) probabilities depending on the which particles are colliding (gluons, photons, protons, etc...), their energies and momenta, whether they have integer spin (boson) or fractional spin (fermion), and other properties too...