The Water Vapor Linestrengths between 11 600 and 12 750 cm-1

The Water Vapor Spectrum in the Region 8600-15 000 cm(-1): Experimental and Theoretical Studies for a New Spectral Line Database

New laboratory measurements are presented for the near-infrared and visible spectrum (8600-15 000 cm(-1)) of water vapor. Spectral line parameters, principally intensities and air-broadening coefficients, are derived from Fourier transform spectroscopic measurements at high resolution (0.03 cm(-1)), a range of optical path lengths (5-513 m), and temperatures of both 252 and 296 K. Experimental line parameters are derived for 5034 assigned transitions and thorough error analysis shows parameter errors of less than 2.5% for one-third and less than 5% for over half of the lines. Calculated spectra, derived using these line parameters, reproduce the original spectra to within 2%. A comparison of the line intensities with those in the HITRAN-96 database identifies large errors in the latter with random differences that exceed a factor of two for many lines, and systematic differences between 6 and 26% depending on the water band under consideration. The recent corrections to the HITRAN database by Giver et al. (J. Quant. Spectrosc. Radiat. Transfer 66, 101-105 (2000)) do not remove these discrepancies and the differences change to 6-38%. The new data are expected to substantially increase the calculated absorption of solar energy due to water vapor in climate models. Copyright 2001 Academic Press.

High-Order Resonances in the Water Molecule

The water-vapor spectra in the near-infrared and visible region were reanalyzed with the purpose of finding experimental evidences of unusual high-order resonance between "dark" high-bending and "bright" stretch vibration states. About 70 transitions to the (050), (060), (070), (080), (160), (061), (170), (071), and, even (0 10 0) bending states, and their resonating partners were assigned in the spectra that gives the experimental energy levels lying near or above the potential energy barrier to linearity. The assignments were confirmed by combination differences and simultaneous observation of both perturbed and perturbing levels. It was found that the high-order resonances 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 scheme originating from well-known Coriolis, Darling-Dennison, and Fermi resonances in H(2)O molecule. Copyright 2001 Academic Press.