Can one determine the dipolar moment of ArH+X1Σ+ from frequency data of pure rotational and vibration-rotational spectra?

On the basis of an objective fit to 443 appraised measurements of frequencies and wave numbers of pure rotational and vibration-rotational transitions of ArH+ in six isotopic variants, 19 fitted parameters – 12 for potential energy and seven for extra-mechanical effects – suffice to reproduce these measurements within experimental uncertainty, σ̂∼1. Careful analysis of these parameters reveals that, whereas a rough estimate of rotational g factor is consistent with both previous experimental and computational results, no sensible estimate of electric dipolar moment is derivable, despite Molskiʹs claim to the contrary [Chem. Phys. Lett. 342 (2001) 293]. Deficiencies of Molskiʹs analysis are discussed.