Using Cu Kα1/Kα2 Splitting and a Powder XRD System To Discuss X-ray Generation

When single crystals are probed by powder X-ray diffraction (PXRD) systems, the peak widths are smaller and signal intensities are greater than those from powdered samples. Instead of the expected single peak, a doublet can be observed, and undergraduate students face a big challenge explaining its origin. This activity is suitable as an inquiry-based, upper-level undergraduate laboratory activity. Students typically engage in an extensive literature search and reading in order to understand observed diffraction data. With a little bit of guidance from the instructor, students can learn how X-rays are generated, and which X-rays are used in PXRD experiments. They can also learn about the electronic transitions in the target electrode leading to characteristic X-rays and learn about the role of spin–orbit coupling.