Ab initio calculations of the rovibrational states of He 2O 2+

Abstract

All-electron CCSD(T)/cc-pCVTZ theory was used to calculate the equilibrium geometry and a 68 point discrete potential energy hypersurface for the dihelium oxene dication He 2O 2+. The CCSD(T) optimised geometry was of C 2v symmetry with an R OHe bond length of 1.168 Å and an included bond angle of 92.6 °. An analytical potential function was obtained from this surface using an Ogilvie Padé (4,5) power series expansion, which yielded a (χ 2) 1 2 value of 2.810 × 10 −5 a.u. The analytical function was then embedded in the Eckart-Watson Hamiltonian, which was solved variationally. Within the anharmonic approximation, the fundamental frequencies for the breathe, bend and asymmetric stretch vibrations were calculated to be 1247.3 cm −1, 816.8 −1 and 1275.6 cm −1, respectively. Using a 560 configuration basis involving products of vibrational eigenfunctions and plus/minus combinations of regular symmetric-top rotor functions, the low-lying rovibrational states of the 1A 1 electronic state of He 2O 2+ were determined.