X-ray notation

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X-ray notation is a method of labeling atomic orbitals that grew out of X-ray science. It is still traditionally used with most X-ray spectroscopy techniques including AES and XPS. In X-ray notation, every principal quantum number is given a letter associated with it.


Quantum Numbers Atomic Notation X-ray Notation
n l s j
1 0 ±1/2 1/2 1s(1/2) K1
2 0 ±1/2 1/2 2s(1/2) L1
2 1 -1/2 1/2 2p1/2 L2
2 1 +1/2 3/2 2p3/2 L3
3 0 ±1/2 1/2 3s M1
3 1 -1/2 1/2 3p1/2 M2
3 1 +1/2 3/2 3p3/2 M3
3 2 -1/2 3/2 3d3/2 M4
3 2 +1/2 5/2 3d5/2 M5


  • X-ray sources are classified by the type of material and orbital used to generate them. For example, Cu X-rays are emitted from the K orbital of copper.
  • X-ray absorption is reported as which orbital absorbed the x-ray photon. In EXAFS and XMCD the L-edge or the L absorption edge is the point where the L orbital begins to absorb x-rays.
  • Auger peaks are identified with three orbital definitions, for example KL1L2. In this case, K represents the hole that is initially present at the core level, L1 the initial state of the electron that relaxes down into the core level hole, and L2 the initial energy state of the emitted electron.

See also[edit]


  1. ^ Dr. Garrett's Class Notes page 12 http://www.cem.msu.edu/~cem924sg/Topic09.pdf Retrieved 10-07-08
  2. ^ IUPAC Table VIII.1 page 5 http://old.iupac.org/reports/V/spectro/partVIII.pdf Retrieved 30-05-09