A new route to the dissociation energy of ionic and neutral HCl via lineshape analysis of single rotational transitions

Abstract

From the analysis of steps observed in single rotational transitions of predissociation spectra the dissociation energy of HCl⁺ has been determined as D_o(HCl⁺) = 37 536.7 ± 0.5 cm⁻¹. Combining this value with accurate literature data on the ionization energy of HCl and Cl we derive a new value for the dissociation energy of neutral HCl, D_o(HCl) = 35 747.2 ± 1.2 cm⁻¹. Finally by combination with the dissociation energy of Cl₂ and H₂ we obtain an improved 0 K heat of formation of HCl, Δ_fH°(HCl, 0 K) = −91.99 ± 0.02 kJ mol⁻¹. These results are believed to be relevant for all thermochemical investigations involving the HCl molecule.