The Vibrational Level Spectrum of H2O(X̃1A′) on a Partridge–Schwenke Potential up to the Dissociation Limit

Abstract

We report accurate vibrational energy levels of H2O(X̃1A′) up to the dissociation limit on a recent ab initio potential energy surface of Partridge and Schwenke. Eigenvalues of the exact vibrational Hamiltonian in the Radau coordinates were obtained using the Lanczos algorithm. To improve computational efficiency, we utilized the extended symmetry-adapted discrete variable representation for the angular kinetic energy operator and adapted the hydrogen exchange symmetry in the radial coordinates using an index-swapping scheme. Normal mode assignments have been made to vibrational levels up to 20 000 cm−1, and several (local mode) stretching overtones up to the dissociation limit have been identified. Agreement with available experimental data is excellent.