High-Order Resonances in the Water Molecule

High sensitivity absorption spectroscopy of HDO by ICLAS-VeCSEL between 9100 and 9640cm−1

“…An unexpected high number (55) of rotational energy levels of the highly excited bending (0 7 0) state could be derived as a consequence of a strong resonance strengthening of the 7m 2 band. This confirms that centrifugal distortion effect in HDO is abnormally strong and leads to considerable perturbation of its rovibrational spectrum at a high excitation of bending vibration [2,26].…”

“…It is based on the usual general principles of resonance interactions: close values of the energy levels of the resonating states, proportionality of the intensities of transitions originating from the same lower state and involving coupled upper levels, as well as some extrapolation of the value of the matrix element of the resonance operator. In particular, this coupling term is believed to increase quickly when a highly excited bending state is involved in the resonance [26]. As stressed in [6], SP rovibrational assignments for the (2 3 0) and (1 5 0) states are often ambiguous.…”

High-Order Resonance Interactions in HDO: Analysis of the Absorption Spectrum in the 14980–15350 cm−1 Spectral Region

“…An interpretation proposed in Refs. (18,20) is that strong centrifugal distortion associated with the bending vibrations may be responsible for such a resonance interaction. However, the origin of the resonances involving highly excited bending states is still far from being completely understood.…”

“…It was, however, experimentally proved for H 2 O and theoretically interpreted as resulting from a rapid increase in the resonance coupling with the bending excitation (18 -20). For the H 2 O species, this coupling was estimated to vary exponentially with the sum of the bending quantum numbers of the resonating states (18). After the determination of the two main resonance partners of the (014) state, we fitted the energy levels of all three interacting states.…”

Water vapour line assignments in the 9250–26000cm−1 frequency range

“…The energy levels of such states give insight into the intramolecular dynamics of water for high excitation of the bending vibration which probes the potential close to linear geometries and which is accompanied by the abnormal centrifugal distortion effects [41]. Direct transitions to these high bending states are weak.…”