Koopmans' theorem

{
  "id": "MLC-T-CHM-006378",
  "term": "Koopmans' theorem",
  "field": "Chemistry",
  "definition": "A theorem in quantum chemistry that states that the negative of the orbital energy of a molecular orbital in a Hartree-Fock calculation approximates the ionization energy for removing an electron from that orbital. This approximation assumes that the remaining electrons do not reorganize upon ionization. It is often used to interpret photoelectron spectra.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "hartree",
    "ionization"
  ],
  "references": [
    "PAC, 1999, 71, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1949 (https://doi.org/10.1351/pac199971101919)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/koopmans-theorem/"
}