Analysis of torsional splittings in the microwave spectra of dimethylether,CH3OCH3 and its isotopes,CD3OCH3 and CD3OCD3

The multiplet splitting patterns of microwave transitions in the ground state and the first two torsional excited states of CH₃OCH₃, CD₃OCD₃, and CD₃OCH₃ were analyzed in terms of the semirigid rotor models C_2vF-C_3vT-C_3vT and $\text{C}{}_3\text{F-}\text{C}{}_{\mathrm{3v}}\text{T-}\text{C}{}_{\mathrm{3v}}\text{T}\text{?}$. The following nonzero potential coefficients were obtained for CH₃OCH₃: V₃₀ = V₀₃ = 909.05 ± 0.49 cm^?1, V′₃₃ = 5.06 ± 1.60 cm^?1; for CD₃OCH₃: V₃₀(CD₃) = 897.18 ± 2.41 cm^?1, V₀₃(CH₃) = 910.45 ± 0.33 cm^?1; for CD₃OCD₃: V₃₀ = V₀₃ = 897.00 cm^?1. These results are compared to earlier microwave studies of these molecules.