Comparison of Spectroscopic Strategies to Determine Molecular Geometries and the Impact of Nuclear versus Atomic Masses: The Example of HCO + and HOC +

Abstract : We compare a recently proposed mixed experimental/theoretical procedure for the derivation of molecular equilibrium structures with several commonly used spectroscopic approaches using experimental data for several isotopologues. We also examine the sensitivity of the results from these approaches to the replacement of the commonly employed atomic masses with nuclear masses. This point is of particular importance for ionic species like HCO + and HOC + which serve as numerical reference cases. The scatter of molecular equilibrium geometries derived by different approaches is found to exceed stated statistical uncertainties by about an order of magnitude.