THE VIBRATIONAL AND TEMPERATURE-DEPENDENCE OF THE MAGNETIC-PROPERTIESOF THE OXONIUM ION (H3O+)

First- and second-order polarization propagator calculations of magnet izability, rotational g-factor, spin-rotation constant, and hydrogen a nd oxygen shielding property surfaces are reported for the gas phase o xonium ion. Using these surfaces and the nonrigid inverter ro-vibratio nal eigenfunctions, effective magnetic molecular constants are obtaine d for the lowest ro-inversional states of (H3O+)-O-17 and (D3O+)-O-17. The predicted constants exhibit sizable and non-monotonic dependence on the vibrational and rotational quantum numbers. We find nearly temp erature independence of both the H-1 and O-17 shieldings, mainly due t o cancellation effects between contributions from the inversional and the symmetric stretching modes. We compute a downfield shift in H-1 as well as O-17 Shieldings of H3O+ relative to pure water in agreement w ith earlier observations. The influence of hydrogen bonding on these s hifts, as well as on the deuterium-induced isotope shifts on the O-17 shielding, is discussed.