# The bremsstrahlung and the atomic number of the element of the target

I came across this question in my text book, it says:

What will happen to the x-rays if we change the element of the target in Coolidge tube by another one with a higher atomic number?

I believe that the characteristic spectrum will have a shorter wavelength, but I don't know whether the bremsstrahlung will be affected or not? And if the bremmstrahlung will undergo a change how would be this? (Note: my book says the bremsstrahlung is affected by the voltage between the cathode and the anode and didn't mention anything about the element of the target material).

• The wikipedia article covers this, perhaps in more depth than you might want. – Jon Custer May 30 '17 at 16:27
• You mean that article with the Köhn-Ebert formulas @JonCuster ? Basic answer is that the short-wave cutoff does not change. Intensity is a bit complicated, because self-absorption is also higher in high-Z materials. – Pieter May 31 '17 at 12:13

As an example for X-ray crystallography, where targets of Molybdenum ($^{42}$Mo) are frequently used as "general workhorse", and Copper ($^{29}$Cu) is more suitable for organic matter, especially proteins, the superposition below may be helpful:
The then selected and used $K_\alpha$ are the at wavelengths of 0.709 (Mo) and 1.54 Å (Cu), respectively.