Project Details:

A database of water transitions from experiment and theory

Project No.:2004-035-1-100
Start date:2005-03-01
End date:2012-01-01
Division:Physical and Biophysical Chemistry Division
Objective:

Critical compilation, experimental determination and validation, and theoretical verification and extension of accurate frequency, energy level, line intensity, line width, and pressure effect spectral parameters of water and all of its major isotopologues.

Description:

The full characterization of the spectrum of water vapor from the microwave to the near ultraviolet is a prerequisite for modeling and understanding of many fields in chemistry, physics and engineering, including (1) atmospheric modeling, with emphasis on the definitive understanding of global warming (water vapor is responsible for about 70 % of the known atmospheric absorption of sunlight and the majority of the greenhouse effect), (2) communication-related fields using the Earth's atmosphere, such as satellites and telecommunication, (3) astronomy, such as that of cool stars (where hot water is a major constituent), (3) water lasers and masers, widespread in outer space, (5) study of comets, based on fluorescence spectroscopy, and (6) combustion research, such as rocket exhausts, forest fires, and turbine engines (hot steam is a major product of most combustion processes).

Water spectra have been the subject of immense scientific effort resulting in a large number of data. They are used mostly without critical evaluation, comparison, and inclusion in annotated databases, an exception being the (room temperature) HITRAN database.

The present collaborative effort is aimed at devising and constructing a database comprising, eventually, the complete linelist of all major isotopologues of water for studies at all temperatures. To achieve this goal this project will bring together researchers from around the globe who are active in studying the rovibrational spectra of water as well as experts in related data handling. The linelist to be compiled will include theoretical and (where available) experimental values of transition frequencies, intensities, and pressure broadening parameters for all major isotopologues. Emphasis will be on validation, comparisons, and test of the database.

Despite a huge effort by experimentalists in the past, a breakthrough and an essential improvement in this field may not be expected in the foreseeable future. There is no hope for a complete experimental characterization of the rovibrational spectra of water isotopologues under hot and cold condition, not least because hot applications require the characterization of up to a billion transitions. Similarly, despite significant progress in the area (see, e.g., Polyansky et al., Science 2003, 299, 539), there exists no complete and accurate theoretical model with which one can predict the high-resolution spectrum of water. Consequently, only a judicious combination of experiment and theory will lead to an understanding of the spectroscopy of water, which is arguably the single most important polyatomic molecule.

Knowledge of the spectral and temperature dependence of the water vapor continuum is important for modeling atmospheric radiative balances. The continuum can be measured using high-sensitivity techniques, such as cavity ring-down spectroscopy. Calculations based upon existing DBs usually substantially underestimate the continuum cross sections, a situation which is to be remedied here.

The first compilation of rovibrational levels of H216O was published recently by members of this Task Group (Tennyson et al., J. Phys. Chem. Ref. Data 2001, 30, 735) proving the feasibility of such an undertaking by a thoughtful combination of experimental and theoretical procedures.

To augment the presently available results a concerted effort including both high-quality experiments to characterize the spectra of water and its isotopologues (using Fourier Transform Spectroscopy, Laser Absorption Spectroscopy, Cavity Ring-Down Spectroscopy, Cavity Enhanced Absorption Spectroscopy, etc., coupled with the use of state-of-the-art techniques for water vapor sample preparation) at a number of wavelengths and temperatures and new theoretical calculations of spectra, based on variational treatments are needed. One particular difficulty to be addressed is the theoretical evaluation of pressure and temperature dependence of spectroscopic line profiles, vitally important for modeling purposes.

To achieve the stated goals of this project requires a concerted effort of experimental and theoretical chemists and physicists, spectroscopists, and computer scientists.

Progress:

June 2009 update - The project has established a protocol for inverting transition frequencies taken from high resolution laboratory spectra to give energy levels. The procedure, called MARVEL (Measured Active Rotational-Vibrational Energy Levels) is based on the use of the so-called X-matrix method which has been in use for sometime for producing energy levels from a single spectrum. Adapting the X-matrix to large datasets of heterogenous data raises a number of issues to do with both consistency of the underlying data and consistency of the published errors. These are addressed in MARVEL itself before and during the inversion process, and post hoc by comparing the MARVEL energy levels with high accuracy variational nuclear motion calculations.

The task group published its first paper [1] both setting out this strategy and applying it the water isotopologues H217O and H218O. Among other things the list of validated energy levels, 2687 for H217O and 4839 for H218O, can be used to give very precise predictions of yet-to-be measured line frequencies.
The active nature of this activity is illustrated by the publication of new spectra subsequent to the completion of this paper. These spectra will be used to update the energy levels and will be published as part of studies on HDO and the main water isotopologue, H216O, which are currenly underway.

[1] J. Tennyson, P.F. Bernath, L.R. Brown, A. Campargue, M.R. Carleer, A.G. Csaszar, R.R. Gamache, J.T. Hodges, A. Jenouvrier, O.V. Naumenko, O.L. Polyansky, L.S. Rothmam, R.A. Toth, A.C. Vandaele, N.F. Zobov, L. Daumont, A.Z. Fazliev, T. Furtenbacher, I.E. Gordon, S. N. Mikhailenko and S. V. Shirin, IUPAC Critical Evaluation of the Rotational-Vibrational Spectra of Water Vapor. Part I. Energy Levels and Transition Wavenumbers for H217O and H218O, J. Quant. Spectrosc. Rad. Transf., 110, 573-596 (2009). DOI:10.1016/j.jqsrt.2009.02.014

> project update report published in Chem. Int. Sept-Oct 2009

Sept 2010 update - The task group applied the MARVEL protocol to the deuterated isotopologues of water. This is the second [2] of a series of articles reporting critically evaluated rotational-vibrational line positions, transition intensities, pressure dependences, and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. This article presents energy levels and line positions of the following singly deuterated isotopologues of water: HD16O, HD17O, and HD18O. The MARVEL (measured active rotational-vibrational energy levels) procedure is used to determine the levels, the lines, and their self-consistent uncertainties for the spectral regions 0 - 22708, 0 - 1674, and 0 - 12 105 cm-1 for HD16O, HD17O, and HD18O, respectively. For HD16O, 54 740 transitions were analyzed from 76 sources, the lines come from spectra recorded both at room temperature and from hot samples. These lines correspond to 36 690 distinct assignments and 8818 energy levels. For HD17O, only 485 transitions could be analyzed from three sources; the lines correspond to 162 MARVEL energy levels. For HD18O, 8729 transitions were analyzed from 11 sources and these lines correspond to 1864 energy levels. The energy levels are checked against ones determined from accurate variational nuclear motion computations employing exact kinetic energy operators. This comparison shows that the measured transitions account for about 86% of the anticipated absorbance of HD16O at 296 K and that the transitions predicted by the MARVEL energy levels account for essentially all the remaining absorbance. The extensive list of MARVEL lines and levels obtained are given in the Supplementary Material of this article, as well as in a distributed information system applied to water, W@DIS, where they can easily be retrieved. In addition, the transition and energy level information for H217O and H218O, given in the first paper of this series [1], has been updated.

[2] J. Tennyson, P.F. Bernath, L.R. Brown, A. Campargue, M.R. Carleer, A.G. Csaszar, L. Daumont, R.R. Gamache, J.T. Hodges, O.V. Naumenko, O.L. Polyansky, L.S. Rothmam, R.A. Toth, A.C. Vandaele, N.F. Zobov, T. Furtenbacher, I.E. Gordon, S.-M. Hu, S. N. Mikhailenko and B.A. Voronin, IUPAC Critical Evaluation of the Rotational-Vibrational Spectra of Water Vapor. Part II. Energy Levels and Transition Wavenumbers for HDO, J. Quant. Spectrosc. Rad. Transf., 111, 2160-2184 (2010). DOI:10.1016/j.jqsrt.2010.06.012.


May 2014 - Part III and IV in the series "IUPAC critical evaluation of the rotational-vibrational spectra of water vapor" are available and published in Journal of Quantitative Spectroscopy and Radiative Transfer

- IUPAC critical evaluation of the rotational-vibrational spectra of water vapor, Part III: Energy levels and transition wavenumbers for H216O
Jonathan Tennyson, et al, Journal of Quantitative Spectroscopy and Radiative Transfer, Vol 117 (March 2013), pp. 29-58. http://dx.doi.org/10.1016/j.jqsrt.2012.10.002

- IUPAC critical evaluation of the rotational-vibrational spectra of water vapor. Part IV. Energy levels and transition wavenumbers for D216O, D217O, and D218O
Jonathan Tennyson, et al, Journal of Quantitative Spectroscopy and Radiative Transfer, Vol 142 (July 2014), pp. 93-108. http://dx.doi.org/10.1016/j.jqsrt.2014.03.019

See continuation as project 2011-022-2-100

last update 20140521

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