Diabatic coupling

{
  "id": "MLC-T-CHM-003118",
  "term": "Diabatic coupling",
  "field": "Chemistry",
  "definition": "The interaction between two or more electronic states that leads to transitions between them, particularly when the Born-Oppenheimer approximation breaks down. This coupling is described by off-diagonal elements in the electronic Hamiltonian matrix, which depend on nuclear coordinates. It is a key concept in understanding non-adiabatic processes in chemical reactions and spectroscopy.",
  "subject": "Physical and Biophysical Chemistry",
  "see_also": [
    "chemical induction"
  ],
  "references": [
    "PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 163 (https://doi.org/10.1351/pac199668010149)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/diabatic-coupling/"
}