AN AB-INITIO STUDY OF MOLECULAR-HYDROGEN AND ITS DEUTERATED ANALOGS PARTIALLY ORIENTED IN NEMATIC LIQUID-CRYSTALS

Thermal expectation values for nuclear magnetic resonance (NMR) observables for molecular hydrogen and its isotopically substituted analogues partially oriented in nematic liquid crystal solvents are calculated from first principles. High-quality nuclear wavefunctions and available data for highly correlated electronic wavefunctions at many different geometries are used from the literature. In the present description vibrational anharmonicity, centrifugal distortion, the changes of the nuclear quadrupole coupling with internuclear distance, and the dependence of the molecular quadrupole moment on the rotational quantum number have been included. The results strongly support previous conclusions that hydrogens in nematic phases are predominantly oriented through the interaction between their molecular quadrupole moment and the non-zero average external electric field gradient present in these solvents. In addition, the present theoretical results provide the basis for obtaining reliable estimates of such average external electric field gradients from a single NMR observable.