The experimental data were reported by
(1) C. A. Gottlieb, T. C. Killian, P. Thaddeus, P. Botschwina, J. Flügge, and M. Oswald, 1993, J. Chem. Phys. 98, 4478.
The predictions are of sufficient accuracy for all radio astronomical purposes.
At low temperatures, it may be necessary to discern between ortho-l-C₃D₂ and para-l-C₃D₂. The ortho states are described by K_a even, the para states by K_a odd. The nuclear spin-weights are 2 and 1 for ortho-l-C₃D₂ and para-l-C₃D₂, respectively.The J_KaKc = 1₁₁ is the lowest para state. It is approximately 5.136 cm^–1 above ground.
The dipole moment was assumed to agree with that of the main isotopic species and was reported in (1).