A note on l-type doubling constants in linear triatomic molecules ClHCl−: A molecular anion with an unusual q

In this note it will be recalled that the sign of the quantity which is called l-type doubling constant in linear triatomic molecules is determined by two factors which are independent. The first factor depends on the construction of the wavefunction describing the rovibrational motion of the linear molecule. The second one is a result of the interplay between the molecular potential energy function and the atomic masses. The latter effect makes in almost all linear triatomic molecules the same contribution to the sign. In this paper an exception to this rule will be presented: ClHCl− shows an unusual l-type coupling constant.