Indirect Spin-Spin Coupling Constants in the Hydrogen Isotopologues

Area of Science:

• Quantum Chemistry
• Spectroscopy
• Nuclear Magnetic Resonance

Background:

• Indirect spin-spin coupling constants are crucial molecular parameters.
• Accurate theoretical calculations and experimental measurements are vital for understanding molecular interactions.

Purpose of the Study:

• To experimentally and theoretically determine indirect spin-spin coupling constants for hydrogen deuteride (HD), hydrogen tritide (HT), and deuterium tritide (DT).
• To compare gas-phase nuclear magnetic resonance (NMR) data with ab initio computations.
• To investigate the influence of nuclear relaxation on NMR spectra and assess agreement between theory and experiment.

Main Methods:

• Gas-phase nuclear magnetic resonance (NMR) spectroscopy at 300 K.
• Ab initio theoretical calculations using the full configuration interaction (FCI) level of theory.
• Analysis of nuclear relaxation effects on NMR spectra.

Main Results:

• Reduced coupling constants were experimentally determined for HD, HT, and DT as 2.338(1), 2.334(3), and 2.316(1) × 10^20 T^2 J^-1, respectively.
• Ab initio calculations yielded values of 2.349(3), 2.343(3), and 2.322(3) × 10^20 T^2 J^-1 for HD, HT, and DT.
• Improved agreement between experimental and theoretical results was observed after accounting for nuclear relaxation.

Conclusions:

• Excellent agreement between experimental and theoretical spin-spin coupling constants for HD, HT, and DT was achieved.
• A minor discrepancy between theory and experiment, beyond estimated error bars, warrants further investigation.
• The study highlights the importance of nuclear relaxation in accurate NMR spectral analysis.