Abstract
An ab initio variational ro-vibration calculation has been performed for the ground electronic state of Na3 +. A discrete potential energy surface was generated using the configuration interaction ansatz, within the frozen-core approximation. An analytical surface was generated from a Padé approximate expansion, which utilized a Dunham expansion variable. The force field was embedded in the Eckart-Watson Hamiltonian from which ro-vibrational wavefunctions and eigenenergies were variationally calculated for the low-lying ro-vibrational states.