Theoretical investigations of the IO,q+ (q = 2, 3, 4) multi-charged ions: Metastability, characterization and spectroscopy
Résumé
Using ab initio methodology, we studied the IOq+ (q = 2, 3, 4) multi-charged ions. Benchmark
computations on the IO(X2) neutral species allow validate the current procedure. For IO2+,
several potential wells were found on the ground and the electronic excited states potentials with
potential barriers with respect to dissociation, where this dication can exist in the gas phase as
long-lived metastable molecules. We confirm hence the recent observation of the dication by mass
spectrometry. Moreover, we predict the existence of the metastable IO3+ trication, where a shallow
potential well along the IO internuclear distance is computed. This potential well supports more
than 10 vibrational levels. The IO3+ excited states are repulsive in nature, as well as the computed
potentials for the IO4+ tetracation. For the bound states, we give a set of spectroscopic parameters
including excitation transition energies, equilibrium distances, harmonic and anharmonic vibrational
terms, and rotational constants. At the MRCI + Q/aug-cc-pV5Z(-PP) level, the adiabatic double
and triple ionization energies of IO are computed to be ∼28.1 eV and ∼55.0 eV, respectively.