K.-F. Song

High-resolution spectroscopy of the triple-substituted isotopologue of water molecule D_{\bf 2}^{\bf 18}O: the first triad

The high-resolution Fourier-transform absorption spectrum of the triple-substituted isotopologue of the water molecule, D O is measured in the 1700–9000 cm−1 region. The transitions of the ν1, 2ν2 and ν3 bands are assigned with the help of the high accuracy variational calculations based on an empirical mass-dependent Partridge–Schwenke potential energy surface. The fittings based on an effective Hamiltonian model are also utilized to confirm the assignments. A set of 816 precise ro-vibrational energy levels for the first triad of interacting vibrational states: (0 0 1), (1 0 0) and (0 2 0) is retrieved. With the upper state combination differences, the ground state energy levels are extended to J max = 23 and . These levels can be used to check the quality of the recently available high accuracy ab initio potential energy surface of the water molecule.