Origin of Characteristic X Rays: How Do Atoms Produce Them?

[Lisa!]

I know the process of their production, now I want to know what's their origin? How does an atom produce them?

PS:Donno whether it's the right forum to ask this question or not, so feel free to move it to the right place!

 

[mgb_phys]

X rays are produced from the inner electrons of an atom. A high energy accelrated electron hits an inner electron in the target atom, it knocks the electron out of the atom and a higher orbital electron falls into the lower orbit giving off energy = an x ray photon.

The energy is characteristic of the energy difference between the levels and so you can tell precisely what atom was involved from the frequency of the emitted x-ray. You can even get hand held x-ray spectrometers the size of a camcorder that you point at a rock or piece of metal and it will tell you the proportion of each element present.

You can also generate x-rays by bremsstrahlung (braking radiation) when the path of a high energy electron bends in an electric or magnetic field

 

[Lisa!]

Thank you but as I said I already know what you said! Souds like I wasn't able to make my question clear.

 

[mgb_phys]

I know the process of their production, now I want to know what's their origin?

surely "process of their production" = origin , what do you want to know?

 

[Lisa!]

surely "process of their production" = origin , what do you want to know?

hmmm...how this difference in binding energy appear as X rays?

 

[Astronuc]

I thought mgb_phys gave a good answer.

X-rays are formed the same way that visible light photons are formed, i.e. an electron falls from one orbit (energy level) to a lower energy orbit (or one more tightly bound) in the atom.

Now the precusor to that is an electron in the K or L shell has to be 'knock out', which can happen with a gamma ray, X-ray of much higher energy than the binding energy of the particular level, or an energetic electron, as is the principal behind an X-ray machine. The first two processes can be photoelectric or Compton effect.

X-rays have characteristic wavelengths related to the atomic electron which falls into the 'open' energy level (K or L shell).

Brehmsstrahlung radiation applies to free electrons, and the X-ray spectrum is continuous.


The distinction between X-rays and gamma-rays has to do with origin rather than energy. X-rays generally refer to photon emissions associated with 'atomic electrons', which gamma-rays refer to photons originating from radionuclei or 'sub-atomic' process, e.g. decay.

Technically, I think brehmsstrahlung photons are considered low energy gamma-radiation, because the electrons are free rather than initially bound.

 

[Renge Ishyo]

The electrons in each atom are at different energy levels, and as they move between levels they emit photons at different frequencies ("colors"). You don't need X-rays to see this phenomenon, just compare visible light emission spectra for different atoms. You will see that the light appears in different places (different distances from the same point of origin) on the spectrum depending on which atom is emitting the light:

http://www.faculty.virginia.edu/consciousness/images/line%20spectra.gif

X-rays are just highly energetic forms of light/energy that are capable of drawing out a line spectrum from an atom as mgb suggests.

 

[malawi_glenn]

There was a thread in the quantum physics subforum about "origin of photons"

 

[Lisa!]

Thank you all, but yet that wasn't anything more than I already knew! Maybe there's nothing more to know about them
Now I have a another question:
Is it possible that an atom absorb a photon, then emit a photon with higher energy?

There was a thread in the quantum physics subforum about "origin of photons"

I guess I should take a look at it!

 

[malawi_glenn]

Lisa, it depends on what state the atom is in when it absorbs the photon..

If it is in its 2nd excited state, then absorb a photon so it can reach he 5th state, then it a possibility that it can decay down to the ground state.. hence the emitted photon has larger energy than what was absorbed. BUT in order to be in the 2nd excited state from the begining, it had to absorb a photon earlier... so the key is Energy Conservation.

 

[Lisa!]

Lisa, it depends on what state the atom is in when it absorbs the photon..

If it is in its 2nd excited state, then absorb a photon so it can reach he 5th state, then it a possibility that it can decay down to the ground state.. hence the emitted photon has larger energy than what was absorbed. BUT in order to be in the 2nd excited state from the begining, it had to absorb a photon earlier... so the key is Energy Conservation.

Aha, thanks! So it doesn't happen for an atom in ground state, is that right?

 

[Redbelly98]

That's right.

 

[Lisa!]

Thank you!