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X-ray notation

X-ray notation is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand X-ray notation rather than just read about it. In short: X-ray notation is a method of labeling atomic orbitals that grew out of X-ray science. Also known as IUPAC notation, it was adopted by the International Union of Pure and Applied Chemistry in 1991 as a simplification of the older Siegbahn notation.

Key takeaways

  • X-ray notation belongs to physics; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect X-ray notation to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of X-ray notation from memory before moving on to harder problems.

Reference excerpt

X-ray notation is a method of labeling atomic orbitals that grew out of X-ray science. Also known as IUPAC notation, it was adopted by the International Union of Pure and Applied Chemistry in 1991 as a simplification of the older Siegbahn notation. In X-ray notation, every principal quantum number is given a letter associated with it. In many areas of physics and chemistry, atomic orbitals are described with spectroscopic notation (1s, 2s, 2p, 3s, 3p, etc.), but the more traditional X-ray notation is still used with most X-ray spectroscopy techniques including AES and XPS.

Conversion

Uses X-ray sources are classified by the type of material and orbital used to generate them. For example, CuKα 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 Siegbahn notation for the names of spectral lines used in X-ray spectroscopy Spectroscopic notation Term symbol notation

References

Worked examples

Example 1 — a first encounter with X-ray notation

Start with the simplest possible case. Write down what X-ray notation claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to X-ray notation before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about X-ray notation ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of X-ray notation

In research
X-ray notation appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses X-ray notation in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
X-ray notation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Atomic physics, X-ray spectroscopy, so understanding it makes those chapters shorter.
In everyday life
Look for X-ray notation outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study X-ray notation in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what X-ray notation means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain X-ray notation out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is X-ray notation in simple terms?

X-ray notation is a method of labeling atomic orbitals that grew out of X-ray science. Also known as IUPAC notation, it was adopted by the International Union of Pure and Applied Chemistry in 1991 as a simplification of the older Siegbahn notation.

Why does X-ray notation matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study X-ray notation?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on X-ray notation.

Tags

  • Atomic physics
  • X-ray spectroscopy

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