Rotational branch

{
  "id": "MLC-T-CHM-010420",
  "term": "Rotational branch",
  "field": "Chemistry",
  "definition": "A family of lines within a gas-phase rovibrational band, all produced by transitions with the same change ΔJ in the rotational quantum number J. In infrared absorption the P, Q and R branches correspond to ΔJ of -1, 0 and +1, whereas vibrational Raman spectra of diatomic molecules show O, Q and S branches with ΔJ of -2, 0 and +2.",
  "subject": "Analytical Chemistry",
  "see_also": [
    "Raman spectroscopy",
    "spectral line",
    "infrared spectroscopy",
    "rotation-vibration spectrum"
  ],
  "references": [
    "PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 762 (https://doi.org/10.1515/pac-2019-0203)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/rotational-branch/"
}