# Koopmans' theorem

> theorem in quantum mechanics that in closed-shell Hartree–Fock theory, the first ionization energy of a molecular system equals the negative of the orbital energy of the highest occupied molecular orbital

**Wikidata**: [Q1422649](https://www.wikidata.org/wiki/Q1422649)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Koopmans'_theorem)  
**Source**: https://4ort.xyz/entity/koopmans-theorem


## References

1. Freebase Data Dumps. 2013