The Intramolecular Structure of Oxonium Ion in Concentrated Aqueous Deuterochloric Acid Solutions

Time-of-flight (TOP) neutron diffraction experiments have been carried out for pure liquid D2O and concentrated aqueous deuterochloric acid solutions (DCl)x(D2O)1−x (x = 0.10, 0.23). The errors due to the inelasticity effect on the molecular structure in the solution were markedly reduced by the TOF measurement at the small scattering angle (2θ=44°). From the least square fit of the theoretical intramolecular interference function to the observed one, the internuclear distances, rOD and rDD, and the root mean square displacements, lOD and lDD, in both D3O+ and D2O molecules were determined as follows; rOD = 1.04(4) Å, rDD = 1.63(5) Å, lOD = 0.07(2) Å and lDD = 0.12(6) Å for D3O+, and rOD = 0.983(5) Å, rDD = 1.55(4) Å, lOD = 0.067(8) Å, and lDD = 0.12(4) Å for D2O. The bond angle ∠DOD in D3O+ was also calculated to be 103°. The trigonal pyramidal structure of oxonium ion in the liquid phase has been lead through this investigation.