Variational calculations of the rovibrational energy levels of K2Na+

Ab initio variational calculations of the low-lying rovibrational states of K2Na+ were performed. A sixth order power series expansion using an exponential Dunham variable was embedded in the Eckart-Watson Hamiltonian, which was solved variationally. The anharmonic fundamental frequencies for the breathe, bend and asymmetric stretch vibrations were calculated to be 188.2 (A1), 78.2 (A1) and 94.9 (B2) cm−1 respectively. The low-lying rovibrational states were calculated using a 560 configuration basis involving products of the vibrational eigenfunctions and plus and minus combinations of regular symmetric-top rotor functions.