Pulse NMR Relaxation Study of Liquid Arsine

Abstract

The arsenic‐proton and arsenic‐deuteron spin‐spin coupling constants in AsH₃ and AsD₃ have been measured using pulse NMR techniques. The accuracy obtainable from this method is found to be comparable to that of other techniques and is applicable in situations where conventional high‐resolution measurements are impossible. A comparison of spin couplings in the Group V hydrides shows that in contrast to the situation in the Group IV hydrides, the reduced spin‐spin coupling constants are relatively constant with increasing Z. Measurement of the arsenic and deuterium spin‐lattice relaxation times over the temperature range $\text{+25}$ to $\text{−113°}\mathrm{C}$ indicates that the arsine molecule reorients as an almost free rotor at high temperatures. The temperature dependence of the proton spin‐lattice relaxation time shows that translational diffusion dominates the relaxation process at low temperatures and that the spin‐rotational interaction becomes an important mechanism at the higher temperatures. The magnitude of the intermolecular contribution to relaxation indicates that translational diffusion proceeds via large‐size jumps of the order of a molecular diameter rather than by small step diffusive motion. These relaxation data also allow the spin‐rotational coupling constant in AsH₃ and the deuteron quadrupole coupling constant in AsD₃ to be determined.