Thermal averaging of the spin-rotation coupling in small molecules leads to an isotropic NMR shielding

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It has been known for over 70 years that nuclear spins couple to molecular rotation via a Zeeman interaction. This spin-rotation coupling can be observed as a discrete splitting in molecular beam magnetic resonance experiments, but is quenched by molecular collisions at higher pressures. We show that because of differential thermal population of M J levels at high magnetic fields, the spin rotation coupling retains a small isotropic component at high field. For all but the smallest molecules at very low temperature, the residual coupling is temperature independent and linear in the magnetic field; it therefore closely mimics the chemical shift. The 'super spin rotation' shift may in the future be a necessary correction to ultra - high precision computations of the NMR chemical shielding of small molecules in gases and liquids.

Original languageEnglish (US)
Pages (from-to)299-303
Number of pages5
JournalJournal of Magnetic Resonance
Issue number2
Publication statusPublished - Oct 1 2011



  • Chemical shielding
  • Gases
  • Molecular g factor
  • NMR
  • Spin-rotation

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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