THEORETICAL INVESTIGATIONS OF THE ELECTRONIC-STRUCTURE OF HEHO+ AND HEHO2+

The (3) Sigma(-) and (1)A' of HeHO+ and (2)A'' ground electronic state s of HeHO2+ have been investigated using the all-electron coupled clus ter single, double, and triple-excitation (CCSD(T)) method coupled wit h an augmented correlation-consistent polarized core valence triple-ze ta basis set (aug-cc-pCVTZ). For the (3) Sigma(-) and (1)A' states of HeHO+, the CCSD(T)/aug-cc-pCVTZ model yielded optimized geometrical pa rameters (r(O-H), r(O-He), theta(H-O-He)) of (1.036 Angstrom, 2.608 An gstrom, 180 degrees) and (1.150 Angstrom, 1.009 Angstrom, 94.7 degrees ) respectively, with the triplet state being more stable by 40.4 kcal mol(-1). For the (2)A'' ground electronic state of HeHO2+, the optimiz ed structural parameters were (1.247 Angstrom, 1.158 Angstrom, 101.3 d egrees) respectively. The calculated harmonic frequencies were real fo r all these states, and their magnitudes were sensitive to the incorpo ration of configuration interaction.