AB-INITIO CALCULATIONS OF THE ROVIBRATIONAL STATES OF HE2O2+

All-electron CCSD(T)/cc-pCVTZ theory was used to calculate the equilib rium geometry and a 68 point discrete potential energy hypersurface fo r the dihelium oxene dication He2O2+. The CCSD(T) optimised geometry w as 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 functi on was obtained from this surface using an Ogilvie Pade (4,5) power se ries 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 Ha miltonian, which was solved variationally. Within the anharmonic appro ximation, the fundamental frequencies for the breathe, bend and asymme tric stretch vibrations were calculated to be 1247.3 cm(-1), 816.8(-1) and 1275.6 cm(-1), respectively. Using a 560 configuration basis invo lving products of vibrational eigenfunctions and plus/minus combinatio ns of regular symmetric-top rotor functions, the low-lying rovibration al states of the (1)A(1) electronic state of He2O2+ were determined.