The far-infrared spectra and ring puckering potential functions of several deuterated analogs of trimethylene sulfide

The far-infrared spectra in the region of 50–200 cm^?1 of several deuterated analogs of trimethylene sulfide (viz α-d₂, β-d₂, α,α′-d₄ and d₆) are reported. The bands are assigned to ring puckering transitions. The potential constants in the function, V(Z) = A(Z⁴ + BZ²), Z the reduced puckering coordinate, were determined for each compound separately. The barrier height, $\text{AB}{}^2\text{4}$, is found to vary upon isotopic substitution in the quadratic-quartic approximation.