Bloch-Siegert shift

{
  "id": "MLC-T-CHM-001376",
  "term": "Bloch-Siegert shift",
  "field": "Chemistry",
  "definition": "A small shift of the resonance frequency of a nuclear spin, caused by the counter-rotating component of a linearly polarized radiofrequency field, which acts as an off-resonant perturbation. The shift grows with the square of the radiofrequency field amplitude and is approximately ω1²/(4ω0), where ω1 is the field strength in angular frequency units and ω0 the Larmor frequency. It is therefore negligible for weak fields in high-field NMR.",
  "subject": "Analytical Chemistry",
  "see_also": [
    "acquisition time",
    "nuclear magnetic resonance spectroscopy",
    "radiofrequency"
  ],
  "references": [
    "PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 682 (https://doi.org/10.1515/pac-2019-0203)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/bloch-siegert-shift/"
}