High-order resonances in the water molecule

The water-vapor spectra in the near-infrared and visible region were reanal yzed with the purpose of finding experimental evidences of unusual high-ord er resonance between "dark" high-bending and "bright" stretch vibration sta tes. About 70 transitions to the (050), (060), (070), (080), (160), (061), (170), (071), and, even (0 10 0) bending states, and their resonating partn ers were assigned in the spectra that gives the experimental energy levels lying near or above the potential energy barrier to linearity. The assignme nts were confirmed by combination differences and simultaneous observation of both perturbed and perturbing levels. It was found that the high-order r esonances with large changing of vibration quantum numbers are typical for the water molecule and they are caused by the strong centrifugal distortion near the linear configuration. These resonances destroy the usual polyad s cheme originating from well-known Coriolis, Darling-Dennison, and Fermi res onances in H2O molecule. (C) 2001 Academic Press.