Tunneling frequencies of NH₂D⁺₂ and CH₂D₂ in crystalline fields of low symmetry Available to Purchase

Procedures for calculating the rotational energy levels of a hindered asymmetric top in crystalline fields of C₃, C₂, and C₁ symmetry are outlined. These procedures are used to compute the splittings between tunneling states of NH₂D⁺₂ and CH₂D₂ in various crystalline environments. These splittings have been computed for NH₂D⁺₂ in (NH₄)₂SiF₆, (NH₄)₂GeF₆, (NH₄)₂TiF₆, NH₄F, NH₄ReO₄, NH₄IO₄, NH₄HF₂, and NH₄ClO₄. Large splittings between tunneling states are computed for this asymmetric top in these compounds, all of which have site symmetries for the ammonium ion that are less than tetrahedral. Two groups of tunneling states are found when the site symmetry of NH₂D⁺₂ is C_3v and four groups of states are found when the site symmetry of NH₂D⁺₂ is S₄, C₂, or C_s. These large tunneling frequencies are similar to those computed for NH₃D⁺ and NHD⁺₃ in these solids. Tunneling frequencies have also been calculated for the asymmetric top CH₂D₂ in phase II of solid methane and for CH₂D₂ adsorbed on the surfaces of graphite and MgO. For the latter two environments, the splittings between the groups of tunneling states are larger than was found for CH₃D, but the tunneling frequencies within a group of tunneling states is smaller than for CH₃D in the same environment.