Rontgen's discovery of x-rays - question

[tramar]

When Rontgen discovered x-rays in 1895, was he witnessing K-shell emission or Brehmsstrahlung radiation?

 

[jtbell]

I don't have a definite answer, but I think I know what you need to look for.

From Yale: An Historical Overview of the Discovery of the X-Ray

From this, it appears that in Röntgen's Lenard tube, the X-rays were produced by cathode rays (electrons) impinging on an aluminum sheet ("window") in the wall of the tube.

If the electron energy is above the K-shell ionization energy for aluminum, then it can kick out a K-shell electron, and you can have K-shell emission.

So you need to find out the K-shell energy for aluminum, and the voltage on Röntgen's Lenard tube (which gives you the energy of the electrons in eV).

Below the K-shell energy, it can be only bremsstrahlung. Above that energy, both processes can take place.

By a strange coincidence, last week, while traveling through Germany, I stood outside the building in Würzburg where Röntgen made his discovery. Unfortunately, the museum inside was closed that day.

 

[Dadface]

If you look at a typical X ray spectrum you will see that it consists of the discrete K,L etc lines superimposed upon a smoothly varying bremmstrahlung background and that most of the energy emitted is in the form of bremmstrahlung.I think Rontgen called them X rays because he didn't know what they were and so he used X, the symbol for the unknown.

 

[jtbell]

Right, in general you have both effects. But if the cathode-ray energy was low enough, then Röntgen would have seen only bremsstrahlung.