The vibrational and temperature dependence of the indirect nuclear spin–spin coupling constants of the oxonium (H 3O +) and hydroxyl (OH −) ions

Abstract

The indirect nuclear spin–spin coupling constants of the gas phase oxonium (H 3O +) and hydroxyl (OH −) ions, their temperature dependence and isotope shifts are predicted by ab initio calculations. The coupling constants are calculated as a function of the symmetric stretching and the inversional coordinates of H 3O + and as a function of the bond length of OH − at the uncorrelated level of the random phase approximation (RPA), at the correlated levels of the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes – SOPPA(CCSD) – and of the multiconfigurational random phase approximation (MCRPA) with a large complete active space wavefunction. Effective ro-vibrational state dependent coupling constants are obtained from these functions and the corresponding ro-vibrational wavefunctions. The effective coupling constants for several states are then used to determine the temperature dependence of the coupling constants. The results are compared with the coupling constants of H 2O and the nuclear magnetic shielding constants of H 3O + and OH −.