Journal of Molecular Spectroscopy 213, 91–121 (2002) doi:10.1006/jmsp.2002.8558 Water Spectra in the Region 4200–6250 cm -1 , Extended Analysis of ν 1 + ν 2 , ν 2 + ν 3 , and 3ν 2 Bands and Confirmation of Highly Excited States from Flame Spectra and from Atmospheric Long-Path Observations S. N. Mikhailenko, ∗,1 VL. G. Tyuterev,† V. I. Starikov, 1 K. K. Albert,‡ B. P. Winnewisser,‡ ,2 M. Winnewisser,‡ ,2 G. Mellau,‡ C. Camy-Peyret,§ R. Lanquetin,§ J.-M. Flaud,¶ and J. W. Brault‖ ∗ Institute of Atmospheric Optics, Russian Academy of Sciences, 1, av.Akademicheskii, 634055 Tomsk, Russia; †Groupe de Spectrom´ etrie Mol´ eculaire et Atmosph´ erique, UMR CNRS 6089, Universit´ e de Reims, Facult´ e des Sciences, Moulin de la Housse, B.P. 1039, 51687 Reims Cedex 2, France; ‡Justus-Liebig-Universit¨ at Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany; §Laboratoire de Physique Mol´ eculaire et Applications, Universit´ e Pierre et Marie Curie, Tour 13, Bte 76, 4 place Jussieu, 75252 Paris Cedex 05, France; ¶Laboratoire de Photophysique Mol´ eculaire, Universit´ e Paris-Sud, Bˆ at. 350, 91405 Orsay, France; and ‖Laboratory for Atmospheric and Space Physics, Campus Box 590, Univ. of Colorado, Boulder, Colorado 80309-0590 Received August 29, 2001; in revised form March 6, 2002 Water vapor infrared spectra have been recorded at room temperature in the range 4200–6250 cm -1 at resolutions (FWHM) between 0.0053 and 0.0080 cm -1 . The use of a White-type multireflection cell made large pressure × pathlength products possible up to 31.27 mbar × 288.5 m. The high signal-to-noise ratio allowed us to observe lines with intensities as small as 10 -26 cm -1 /molecule cm -2 at T = 296 K. Among about 5100 recorded water lines, about half of which are reported for the first time, 2351 lines have been assigned to the second triad of H 2 16 O (bands ν 1 + ν 2 , ν 2 + ν 3 , and 3ν 2 ). This has allowed the determination of line positions and corresponding upper rovibrational states with considerably improved accuracy. The assignments of certain highly excited states have been confirmed by the analysis of flame spectra and hot emission spectra. New values of effective Hamiltonian parameters for the upper states {(110), (030), (011)} have been determined. The generating function model was used in the data reduction to account for the anomalously strong centrifugal distortion of the rovibrational levels and resonance interactions. The RMS standard deviation of the least-squares fit of the assigned H 2 O data was 5 × 10 -3 cm -1 for line positions and 7 × 10 -3 cm -1 for energy levels up to J max = 20 and K a(max ) = 13. Particular attention was paid to water lines in the transparency window 4200–5000 cm -1 , in which existing databases are not sufficient. In this region, 1395 lines of four isotopic species of water have been recorded and over 900 accurate line positions of nine bands of H 2 16 O (ν 1 , ν 3 ,2ν 2 , ν 1 + ν 2 , ν 2 + ν 3 ,3ν 2 ,4ν 2 - ν 2 ,2ν 2 + ν 3 - ν 2 , ν 1 + 2ν 2 - ν 2 ) are reported in this range. A comparison of laboratory spectra with long path atmospheric spectra (20 km slant path in the mountains) in this region shows that many lines missing from available spectroscopic compilations (or considerably shifted compared to observations) are important for a proper interpretation of atmospheric observations. A comparison of the observed data with the best available predictions from the molecular electronic potential energy surface is discussed. C  2002 Elsevier Science (USA) Key Words: IR spectroscopy; water; H 2 O; H 2 16 O; nonrigid molecules; centrifugal distortion; resonances; rovibrational levels; transparency window. 1. INTRODUCTION High-resolution measurements and analysis of water bands in the 1.5–2.5 µm region performed up to 1977 by Pugh and Rao (1, 2) and by Camy-Peyret, and co-workers (3–7 ) were the original basis for several line parameter compilations for water including HITRAN (8) and GEISA (9). The improvement of sensitivity and spectral resolution since that time has stimulated 1 To whom correspondence should be addressed. Fax: 7-382-2-25-90-86. E-mail: semen@lts.iao.ru. 2 Current address: Department of Physics, The Ohio State University, Columbus, Ohio 43210. Supplementary data for this aricle are available on IDEAL (http://www. idealibrary.com) and as part of the Ohio State University Molecular Spec- troscopy Archives (http://msa.lib.ohio-state.edu/jmsa hp.htm). extensive new Fourier transform spectroscopy (FTS) measure- ments. Accurate long-path room temperature measurements in lower (10–13) and higher wavenumber (14–16) ranges have been recently reported. In addition, very high J and K a rotational energy states have been studied through high-temperature mea- surements (17–23), but except for a paper (19) on sunspot spec- tra assignment in a relatively narrow interval, 4600–5100 cm -1 , they mainly pertained to other wavenumber ranges. The main purpose of the present work is the improvement of water vapor line positions in the spectral range 4200–6250 cm -1 and partic- ularly in the 2.5-µm transparency window, generally defined as 4200–5000 cm -1 , useful for atmospheric applications. The anal- ysis of infrared measurements obtained with the Fourier trans- form spectrometer at the Justus-Liebig-Universit¨ at in Giessen is presented here. Among a total of about 5100 lines recorded in 91 0022-2852/02 $35.00 C  2002 Elsevier Science (USA) All rights reserved.