Non-crossing rule

{
  "id": "MLC-T-CHM-008013",
  "term": "Non-crossing rule",
  "field": "Chemistry",
  "definition": "A principle stating that potential energy surfaces of the same symmetry cannot intersect. This rule applies to diatomic molecules and is a consequence of quantum mechanics, specifically the Born-Oppenheimer approximation. It implies that as two atoms approach each other, their electronic states will repel rather than cross if they share the same symmetry.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "reaction coordinate"
  ],
  "references": [
    "PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 374 (https://doi.org/10.1351/pac200779030293)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/non-crossing-rule/"
}