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 2p(1/2) L2
2 1 +1/2 3/2 2p(3/2) 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 core level hole, L1 the relaxing electron's initial state, and L2 the emitted electron's initial energy state.

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