Optical nuclear polarization for sensitivity enhancement of2H NMR single-crystal studies

A gain in detection sensitivity of more than three orders of magnitude is achieved in high-resolution solid-state²H nuclear magnetic resonance of monocrystalline fluorene-d₁₀ by applying optical nuclear polarization via excited triplet states of acridine-h₉ guest molecules. The sensitivity gain is utilized to measure the angular dependence (rotation pattern) of the²H nuclear magnetic resonance lines. In this way the principal values and orientations of all²H quadrupolar tensors are determined. Except for the methylene deuterons, all tensors belonging to the same molecule have one principal axis in common, namely the axis perpendicular to the molecular plane, showing that in the crystal lattice the fluorene molecule is in a planar configuration.