# Photoionization
Canonical mAtlas concept record.
- **Concept ID:** `photoionization`
- **Canonical page:** https://atlas.madvay.com/concepts/photoionization/
- **Interactive graph:** https://atlas.madvay.com/?node=photoionization
- **Content version:** `2.3.0`
- **Primary field:** [Physics](https://atlas.madvay.com/physics/)
- **Fields:** [Physics](https://atlas.madvay.com/physics/), [Chemistry](https://atlas.madvay.com/chemistry/)
- **Primary domain:** [Atomic & molecular physics](https://atlas.madvay.com/physics/atomic-molecular-physics/)
- **Domains:** [Atomic & molecular physics](https://atlas.madvay.com/physics/atomic-molecular-physics/), [Quantum chemistry & spectroscopy](https://atlas.madvay.com/chemistry/quantum-chemistry-spectroscopy/), [Electromagnetism](https://atlas.madvay.com/physics/electromagnetism/)
- **Concept type:** Photon-induced atomic ionization
- **Alternate terminology:** No alternate terminology is currently authored for this record.
## Summary
The ionization of an atom or ion by absorption of a photon, producing an ion and a continuum electron when energy and selection conditions permit.
## Concept sources

- [Wikipedia — Photoionization](https://en.wikipedia.org/wiki/Photoionization) — Photoionization (encyclopedic reference; source ID `wp-physics-photoionization`)
- [NIST — Atomic Spectroscopy: An Introduction](https://physics.nist.gov/Pubs/AtSpec/AtSpec.PDF) — Atomic Spectroscopy: An Introduction (NIST technical reference; source ID `nist-atomic-spectroscopy`)
- [Cambridge — Quantum Mechanics](https://www.damtp.cam.ac.uk/user/tong/quantum.html) — Quantum Mechanics (University of Cambridge lecture notes; source ID `tong-quantum`)

## Incoming relations (arrows to this concept)

### Electromagnetic radiation → Photoionization

- **Relation URL:** https://atlas.madvay.com/concepts/photoionization/#relation-electromagnetism_radiation_to_photoionization
- **Relation ID:** `electromagnetism_radiation_to_photoionization`
- **Direction:** [Electromagnetic radiation](https://atlas.madvay.com/concepts/electromagnetic_radiation/) → [Photoionization](https://atlas.madvay.com/concepts/photoionization/)
- **Relation type:** Physical interaction / binding (`couples-interacts`)
- **Endpoint roles:** source is Interacts with / binds; target is Interacts with / bound by.
- **Authored annotation:** supplies ionizing photons

**Authored explanation:** When photon energy exceeds an applicable ionization threshold and the transition matrix element is nonzero, electromagnetic radiation can eject a bound electron from an atom or ion.

**Edge-type interpretation:** The source field, particle, charge, current, or interaction couples to, acts on, binds, forms, or stabilizes the target in the stated regime. The edge label and detail must identify the exact coupling, interaction, or binding claim and its qualifications.

**Relation sources:**
- [NIST — Atomic Spectroscopy: An Introduction](https://physics.nist.gov/Pubs/AtSpec/AtSpec.PDF) — Atomic Spectroscopy: An Introduction (NIST technical reference; source ID `nist-atomic-spectroscopy`)
- [Cambridge — Quantum Mechanics](https://www.damtp.cam.ac.uk/user/tong/quantum.html) — Quantum Mechanics (University of Cambridge lecture notes; source ID `tong-quantum`)

### Atomic ionization → Photoionization

- **Relation URL:** https://atlas.madvay.com/concepts/photoionization/#relation-atomic_ionization_process_to_photoionization
- **Relation ID:** `atomic_ionization_process_to_photoionization`
- **Direction:** [Atomic ionization](https://atlas.madvay.com/concepts/ionization_process/) → [Photoionization](https://atlas.madvay.com/concepts/photoionization/)
- **Relation type:** Classification (`classification`)
- **Endpoint roles:** source is Has subtype; target is Classified as.
- **Authored annotation:** photon-induced ionization

**Authored explanation:** Photoionization is the subclass of atomic ionization driven by photon absorption, distinguished from collisional, field, or other ionization mechanisms.

**Edge-type interpretation:** The target is a member or subtype of the broader source class.

**Relation sources:**
- [NIST — Atomic Spectroscopy: An Introduction](https://physics.nist.gov/Pubs/AtSpec/AtSpec.PDF) — Atomic Spectroscopy: An Introduction (NIST technical reference; source ID `nist-atomic-spectroscopy`)
- [Cambridge — Quantum Mechanics](https://www.damtp.cam.ac.uk/user/tong/quantum.html) — Quantum Mechanics (University of Cambridge lecture notes; source ID `tong-quantum`)

## Outgoing relations (arrows from this concept)

No direct outgoing relations are authored for this concept.

## License and attribution

License URL: https://creativecommons.org/licenses/by-sa/4.0/

mAtlas - Copyright (c) 2026 Advay Mengle - https://atlas.madvay.com/concepts/photoionization/index.html.md