The CC bond of the molecule has double bond character. Therefore, the molecule is better viewed as chloroethenylidenyl or chlorovinylidenyl rather than chloroethynyl. It is probably slightly non-linear; the structure originates from strong vibronic interaction between a ²Σ and a ²Π state only slightly higher in energy. Several components of the two lowest rotational transitions have been reported by
(1) Y. Sumiyoshi, T. Ueno, and Y. Endo, 2003, J. Chem. Phys. 119, 1426.
These levels are well described by a ²Σ Hamiltonian. No reliable information is available on higher K levels.
Predictions may be sufficiently reliable up to about 100 GHz.
The ab initio a-dipole moment component was reported in (1). Its magnitude depends strongly on the degree of Σ and Π character in this K level.