Water line parameters for weak lines in the range 7400-9600 cm(-1)

A long pathlength, Fourier transform spectrum of pure water vapour [J. Mol. Spectrose. 211 (2002) 169] has been fitted and analysed. Line centres, intensities, and self-broadening parameters have been obtained for about 3900 lines with intensities less then 1 X 10(-24) cm/molecule. Transitions to 240 newly observed energy levels of H2O have been identified. 855 lines have been assigned to three other major isotopologues of water. It is pointed out that a new intensity measurements are needed for the stronger lines in this region. (c) 2005 Elsevier Inc. All rights reserved

Continuous-wave cavity ringdown spectroscopy of the 8 nu polyad of water in the 25 195-25 340 cm(-1) range

State-of-the-art experiments and calculations are used to record and assign the data obtained in the weakly absorbing blue energy region of the H2O spectrum. Continuous-wave cavity ringdown absorption spectroscopy with Doppler resolution is used to probe the range from 25 195 to 25 470 cm(-1) with an absorption sensitivity of similar to 1 parts per 10(9) (ppb)/cm. 62 lines of the polyad nu(OH)=8 are reported, of which 43 are assigned using variational nuclear calculations. The study includes absorption line intensities (in the range of 10(-28)-10(-26) cm/molecule) for all lines and self-broadening pressure coefficient for a few lines. The newly obtained energy levels are also reported. (c) 2005 American Institute of Physics

Water line intensities in the near-infrared and visible

Water is the single most important molecule for models of the earth's atmosphere but line parameters for water, particularly at shorter wavelengths, are difficult to measure reliably. We suggest that the most reliable way of generating water line parameters is to combine data obtained from a variety of sources, thereby separating line parameter determination into results for strong lines, for weak lines and for isotopically substituted water. Theoretical considerations which are addressed include line assignments and labeling of energy levels and the prospects of a full theoretical solution to the water vapor problem. Particular attention is paid to strong line absorption intensities in the near-infrared where recent studies have given significantly different results. The experimental data used to construct the ESA-WVR linelist (J. Mol. Spectrosc. 208 (2001) 32) is re-analyzed with a focus on effects due to pressure determination in the cell, subtraction of the baseline and parameterization of the line profiles. A preliminary re-analysis suggests that the line intensities given by the ESA-WVR study should be closer to those of Brown et al. (J. Mol. Spectrosc. 212 (2002) 57) used in the HITRAN. This shows the vital importance of validating the data for water by independent means. (C) 2003 Elsevier Ltd. All rights reserved

The impact of new water vapor spectroscopy on satellite retrievals

Water vapor, arguably the most important trace gas constituent of Earth atmospheric physics, is also both a retrieval goal and a hindrance in the retrievals of other trace gases from nadir-measuring satellite spectrometers. This is because the atmospherically-attenuated solar spectrum in the visible and shortwave infrared is littered with water vapor bands. The recent plethora of water vapor spectroscopy databases in this spectral region has prompted us to study their utility in satellite retrievals. We consider water vapor spectroscopy compiled from four sources including new spectroscopy due to University College London and Imperial College London. Radiative transfer models of satellite measurements, in combination with accurate retrieval techniques, are quite sensitive to the accuracy and completeness of the water vapor spectroscopy. Notwithstanding the high degree of variability of a number of different factors in satellite measurements we show that retrievals are sensitive to database differences which suggests that our knowledge of water vapor spectroscopy is not as yet complete. In addition, new laboratory measurements indicate that the role of both the far-line wings of water vapor and the cumulative effect of many weak lines each have an important role to play in forming the so-called continuum

Water vapour line assignments in the 9250-26 000 cm (-1) frequency range

Line parameters for water vapour in natural abundance have recently been determined for the 9250-13 000 cm(-1) region [M.-F. Wrienne, A. Jenouvrier, C. Hermans, A.C. Vandaele, M. Carleer, C. Clerbaux, P.-F. Coheur, R. Colin, S. Fally, M. Bach, J. Quant. Spectrosc. Radiat. Transfer 82 (2003) 99] and the 13 000-26 000 cm(-1) region [P.-F. Coheur, S. Fally, M. Carleer, C. Clerbaux, R. Colin, A. Jenouvrier, M.-F. Wrienne, C. Hermans, A.C. Vandaele, J. Quant. Spectrosc. Radial. Transfer 74 (2002) 493] using a high-resolution Fourier-transform spectrometer with a long-path absorption cell. These spectra are analysed using several techniques including variational line lists and assignments made. In total, over 15 000 lines were assigned to transitions involving more than 150 exited vibrational states of (H2O)-O-16. Twelve new vibrational band origins are determined and estimates for a further 16 are presented. (c) 2005 Elsevier Inc. All rights reserved

Dipole moments of highly vibrationally excited water

The intensity of water absorption in the region of the solar spectrum plays a dominant role in atmospheric energy balance and hence strongly influences climate. Significant controversy exists over how to model this absorption accurately. We report dipole moment measurements of highly vibrationally excited water, which provide stringent tests of intensities determined by other means. Our measurements and accompanying calculations suggest that the best currently available potential and dipole surfaces do not accurately model intensities in the optical spectrum of water

Application of renormalized coupled-cluster methods to potential function of water

Abstract The goal of this paper is to examine the performance of the conventional and renormalized single-reference coupled-cluster (CC) methods in calculations of the potential energy surface of the water molecule. A comparison with the results of the internally contracted multi-reference configuration interaction calculations including the quasi-degenerate Davidson correction (MRCI(Q)) and the spectroscopically accurate potential energy surface of water resulting from the use of the energy switching (ES) approach indicates that the relatively inexpensive completely renormalized (CR) CC methods with singles (S), doubles (D), and a non-iterative treatment of triples (T) or triples and quadruples (TQ), such as CR-CCSD(T), CR-CCSD(TQ), and the recently developed rigorously size extensive extension of CR-CCSD(T), termed CR-CC(2,3), provide substantial improvements in the results of conventional CCSD(T) and CCSD(TQ) calculations at larger internuclear separations. It is shown that the CR-CC(2,3) results corrected for the effect of quadruply excited clusters through the CR-CC(2,3)+Q approach can compete with the highly accurate MRCI(Q) data. The excellent agreement between the CR-CC(2,3)+Q and MRCI(Q) results suggests ways of improving the global potential energy surface of water resulting from the use of the ES approach in the regions of intermediate bond stretches and intermediate energies connecting the region of the global minimum with the asymptotic regions