Historical question concerning Moseley's experiment

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SUMMARY

Moseley's experiments in 1913 established a relationship between the square root of the frequency of characteristic X-rays and atomic numbers, utilizing a Bragg diffractometer with potassium ferrocyanide crystals. The choice of potassium ferrocyanide over simpler alternatives like NaCl was driven by the need to maximize the signal-to-noise ratio, ensuring strong reflections of characteristic lines while minimizing Bremsstrahlung interference. The crystal's highly planar single-crystal surface and appropriate plane spacing were critical for achieving optimal results in X-ray measurements.

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jdlawlis
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This question may be beyond the scope of this forum, but I'll give it a go anyway. Moseley's landmark experiments in 1913 related the square root of the frequency of characteristic X-rays of an element to integer values, which he equated to the element's atomic number. He measured the wavelength of this X-ray radiation using a Bragg diffractometer equipped with a potassium ferrocyanide crystal. My question is why he would choose a complicated crystal structure like potassium ferrocyanide instead of something simpler such as NaCl? I highly recommend the following website, which has an online version of Moseley's original paper:

http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Moseley-article.html
 
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jdlawlis said:
My question is why he would choose a complicated crystal structure like potassium ferrocyanide instead of something simpler such as NaCl?
Mostly, I imagine, the reason would have been to maximize signal to noise ratio. So, you want a highly planar single-crystal surface and you want reasonably strong reflections of characteristic lines at angles where reflection of Bremsstrahlung is small. ie: You want a high structure factor for the right plane spacing (to ensure the latter) and you want the planes with these spacings to be cleavage planes of the crystal (for the former requirement).