Ab initio calculations of the rovibrational states of He2O2+

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 He2O2+. The CCSD(T) optimised geometry was of C-2v symmetry with an R(O-He) bond length of 1.168 Angstrom and an included bond angle of 92.6 degrees. An analytical potential function was obtained from this surface using an Ogilvie Pade (4,5) power series expansion, which yielded a (chi(2))(1/2) value of 2.810 x 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 (1)A(1) electronic state of He2O2+ were determined.