This paper describes the status of the 2004 edition of the HITRAN molecular spectroscopic database. The HITRAN compilation consists of several components that serve as input for radiative transfer calculation codes: individual line parameters for the microwave through visible spectra of molecules in the gas phase; absorption cross-sections for molecules having dense spectral features, i.e., spectra in which the individual lines are unresolvable; individual line parameters and absorption cross-sections for bands in the ultra-violet; refractive indices of aerosols; tables and files of general properties associated with the database; and database management software. The line-by-line portion of the database contains spectroscopic parameters for 39 molecules including many of their isotopologues.The format of the section of the database on individual line parameters of HITRAN has undergone the most extensive enhancement in almost two decades. It now lists the Einstein A-coefficients, statistical weights of the upper and lower levels of the transitions, a better system for the representation of quantum identifications, and enhanced referencing and uncertainty codes. In addition, there is a provision for making corrections to the broadening of line transitions due to line mixing. (C) 2005 Elsevier Ltd. All rights reserved.

Precise intensities, self-broadenings and shifts have been obtained for the 12C16O v=2←0 band from simultaneous fits of low-noise, high-resolution Fourier-transform spectra at pressures from 27 to 80kPa (200–600 Torr). Observed line shapes exhibit deviations on the order of 1% from the conventional Voigt profile, primarily due to speed-dependent broadening and secondarily to line mixing. Dicke narrowing is reduced by over an order-of-magnitude from the diffusion value, presumably because of correlations between velocity- and phase-changing collisions.

Absolute line intensities, band intensities, and Herman-Wallis parameters were measured for the (01(1)2)(I)<--(00(0)0) perpendicular band of (CO2)-C-12-O-16 centered at 5315 cm(-1), along with the three nearby associated hot bands: (10(0)2)(II)<-- (01(1)0)(I) at 5248 cm(-1), (02(2)2)(I)<--(01(1)0)(I) at 5291 cm(-1), and (10(0)2)(I)<--(01(1)0)(I) at 5349 cm(-1). The nearby parallel hot band (30(0)1)(I)<--(10(0)0)(II) at 5218 cm(-1) was also included in this study.The rotationless band intensities at 296 K are, respectively,[GRAPHICS](C) 2003 Elsevier Science Ltd. All rights reserved.

Belmiloud, et al have recently suggested that the HITRAN line intensities in the 1130 nm water vapor band are much too weak. Giver, et at corrected unit conversion errors to make the HITRAN intensities compatible with the original measurements of Mandin, et al, but Belmiloud, et al believe that many of those line intensity measurements were too weak, and they propose the total intensity of the 1130 nm water vapor band is 38% stronger than the sum of the HITRAN line intensities in this region. We have made independent assessments of this proposal using 2 spectra obtained with the Ames 25 meter base path White cell. The first was made using the moderate resolution (8 nm) solar spectral flux radiometer (SSFR) flight instrument with a White cell absorbing path of 506 meters and 10 torr water vapor pressure. Modeling this spectrum using the HITRAN linelist gives a reasonable match, and the model is not compatible when the HITRAN line intensities are increased by 38%. The second spectrum was obtained with a White cell path of 1106 meters and 12 torr water vapor pressure, using a Bomem FTIR with near Doppler width resolution. This spectrum is useful for measuring intensities of isolated weak lines to compare with the measurements of Mandin, et al. Unfortunately, as Belmiloud et al point out, at these conditions the strong lines are much too saturated for good intensity measurements. Our measurements of the weak lines are in reasonable agreement with those of Mandin, et al. Neither of our spectra supports the proposal of Belmiloud et al for a general 38% increase of the absorption intensity in the 1130 nm water vapor band.

The rotationless transition moment squared for the x(sup 1) sigma (sup +) v=3 (left arrow) v=0 band of CO is measured to be the absolute value of R (sub 3-0) squared = 1.7127(25)x 10(exp -7) Debye squared. This value is about 8.6 percent smaller than the value assumed for HITRAN 2000. The Herman-Wallis intensity factor of this band is F=1+0.01168(11)m+0.0001065(79)m squared. The determination of self-broadening coefficients is improved with the inclusion of line narrowing; self-shifts are also reported.

We have used the solar spectral flux radiometer (SSFR) flight instrument with the Ames 25 meter base-path White cell to obtain about 20 moderate resolution (8 nm) pure water vapor spectra from 650 to 1650 nm, with absorbing paths from 806 to 1506 meters and pressures up to 14 torr. We also obtained a set at 806 meters with several different air-broadening pressures. Model simulations were made for the 940, 1130, and 1370 nm absorption bands for some of these laboratory conditions using the Rothman, et al HITRAN-2000 linelist. This new compilation of HITRAN includes new intensity measurements for the 940 nm region. We compared simulations for our spectra of this band using HITRAN-2000 with simulations using the prior HITRAN-1996. The simulations of the 1130 nm band show about 10% less absorption than we measured. There is some evidence that the total intensity of this band is about 38% stronger than the sum of the HITRAN line intensities in this region. In our laboratory conditions the absorption depends approximately on the square root of the intensity. Thus, our measurements agree that the band is stronger than tabulated in HITRAN, but by about 20%, substantially less than the published value. Significant differences have been shown between Doppler-limited resolution spectra of the 1370 nm band obtained at the Pacific Northwest National Laboratory and HITRAN simulations. Additional new intensity measurements in this region are continuing to be made. We expect the simulations of our SSFR lab data of this band will show the relative importance of improving the HITRAN line intensities of this band for atmospheric measurements.

The absolute rotationless transition moment squared for the X1Σ+v=3←v=0 band of CO is measured to be |R3–0|2=1.713 (−20, +33)×10−7 Debye2. This value is about 8.6% smaller than the value assumed for HITRAN 2000. The measured Herman–Wallis intensity factor of this band is F=1+0.01168(11)m+0.0001065(79)m2. The determination of self-broadening coefficients is improved with the inclusion of line narrowing; self-shifts are also reported.

Several groups have recently been working to improve the near-infrared spectrum of water vapor on HITRAN. The unit-conversion errors found by Giver, et al have now been corrected on the recently released HITRAN-2000. The most important aspect of this article for atmospheric absorption was increasing all the HITRAN-1996 intensities of the 940 nm band by nearly 15%. New intensity measurements of this band by Brown, et al (submitted to J. Mol. Spec.) have now been included in the latest HITRAN. However, Belmiloud, et al discuss new data in the 633-1175 nm region which they expect will substantially increase the calculated absorption of solar radiation by water vapor. They suggest the 4 bands at 725, 820, 940, and 1130 nm are all stronger than the sum of the line intensities currently on HITRAN. For the 725 and 820 nm bands, their recommended intensity increases are 10% and 15%, about the same as previously noted by Grossmann and Browell and Ponsardin and Browell. Belmiloud, et al only suggest a 6% increase for the 940 nm. band over the corrected HITRAN-1996 intensities, but a large 38% increase for the 1130 nm band. The new data discussed by Belmiloud, et al have now been published in greater detail by Schermaul, et al. The intensity increase for the 1130 nm band discussed by Belmiloud, et al is very substantial; it is important to quickly determine if the HITRAN intensity values are in error by as much as they claim. Only intensity errors for the strong lines could result in the total band intensity being in error by such a large amount. To quickly get a number of spectra of the entire near-infrared region from 650 to 1650 nm, we used the Solar Spectral Flux Radiometer with our 25-meter base path White absorption cell. This moderate resolution spectrometer is a flight instrument that has flown on the Sandia Twin Otter for the ARESE 11 experiment. The measured band profiles were then compared to calculated spectra using the latest HITRAN line intensities, convolved with the instrumental resolution. Our spectra for the 725 and 820 nm bands show somewhat more absorption than the HITRAN simulations, about as expected by Belmiloud, el al. The total absorption for our spectra of the 940 nm band agrees well with the HITRAN simulations; this HITRAN spectral region now has the new measurements of Brown, et al. Our spectra of the 1130 nm band have somewhat more absorption than the HITRAN simulations, but not as much as the 38% intensity increase for this band suggested by Belmiloud, et al. An intensity increase of about 20% on average would be more compatible with our data. Finally, our spectra of the 1370 nm band are fairly well modeled by the HITRAN simulations, despite the known problems of the older HITRAN data in this region.

Corrections have recently been reported (Giver et al.) on the short-wave (visible and near-infrared) line intensities of water vapor that were catalogued in the spectroscopic database known as HITRAN. These updates have been posted on www.hitran.com, and are being used to reanalyze the polar stratospheric absorption in the 0.94 microns band as observed in POAM. We are currently investigating additional improvement in the 1.13 microns band using data obtained by us with an absorption path length of 1.107 km and 4 torr of water vapor and the ab initio line list of Partridge and Schwenke (needs ref). We are proposing the following four types of improvement of the HITRAN database in this region: 1) HITRAN has nearly 200 lines in this region without proper assignments of rotational quantum levels. Nearly all of them can now be assigned. 2) We have measured positions of the observable H2O-17 and H2O-18 lines. These lines in HITRAN currently have approximate positions based upon rather aged computations. 3) Some additional lines are observed and assigned which should be included in the database. 4) Corrections are necessary for the lower state energies E" for the HITRAN lines of the 121-010 "hot" band.

Absolute line intensities of (12)C(16)O(2) are experimentally measured for the first time for the (00(0)3)(I) <-- (10(0)0)(II) band at 5687.17 cm(-1) and the (00(0)3)(I) <-- (10(0)0)(I) band at 5584.39 cm(-1). The spectra were obtained using a Bomem DA8 Fourier transform spectrometer and a 25-m base-path White cell at NASA-Ames Research Center. The rotationless bandstrengths at a temperature of 296 K and the Herman-Wallis parameters are S(0)(vib) = 6.68(30) x 10(-25) cm(-1)/(molecule/cm(2)); A(1) = 1.4(9) x 10(-4), and A(2) = -1.1(5) x 10(-5) for the (00(0)3)(I) <-- (10(0)0)(II) band and S(0)(vib) = 6.07(22) x 10(-25) cm(-1)/(molecule/cm(2)); A(1) = 5.2(1.5) x 10(-4) and A(2) = -4.0(7) x 10(-5) for the (00(0)3)(I) <-- (10(0)0)(I) band.

Systematic differences are apparent between the absolute intensities of water vapor lines in the 8036–22,657 cm−1 region listed in the HITRAN-96 database and those reported in the five original articles which constitute the sources for the database. This note suggests corrections which should be made to the HITRAN line intensities of various water bands in this region to achieve compliance with the measured intensities. A correction which increases the intensities by 8–14% should be applied in the 9500–12,861 cm−1 region. The correction decreases the line intensities in the 8036–9482 and 13,200–22,657 cm−1 intervals. The correction factor is exp[−E″(2hc/k)(1/T−1/T′)] in these regions, where T=296 K and T′ is the measurement temperature. This correction becomes significant at higher values of E″; it decreases the line intensities in HITRAN by about 19% at E″=1400cm−1.

The absolute intensities of transitions in the 2ν3 vibrational band of 12C16O17O at 4655.2cm−1 have been measured in natural isotopic abundance; the spectra being obtained with a resolution of 0.012cm−1 using a Bomem DA8 FTS at NASA/Ames and the McMath FTS at Kitt Peak National Observatory, AZ. About 45 transitions were fitted to obtain the rotationless band strength of S0vib = 8.489 × 10−25cm−1/(molecule/cm2) at 296K. Although the current HITRAN line positions for this band do not have any defined uncertainties, our measurements average only about 0.0025cm−1 smaller.

The absolute intensities of transitions in the 2ν3 vibrational band of 12C16O18O at 4639.5cm-1 have been measured in natural isotopic abundance; the spectra were obtained with 0.012cm-1 resolution using the McMath Fourier transform spectrometer of the National Solar Observatory located at Kitt Peak National Observatory. About 70 transitions have been fitted with an rms deviation of approximately 1.5% to obtain the rotationless band strength of S0vib=1.442×10-23cm molecule-1 at 296K along with a small first-order Herman–Wallis parameter of A1=3.5×10-5; higher order Herman–Wallis parameters could not be determined. The measured line positions, obtained using the CO2 gas samples in the range of 45–65Torr at room temperature, confirm the current HITRAN tabulated values. The internal precision of our intensity measurements is very high, and the uncertainty due to possible systematic errors is judged to be less than ±3%.

This work was initiated to compare absolute line intensities retrieved with the Kitt Peak FTS (Fourier Transform Spectrometer) and Ames BOMEM FTS. Since thermal contaminations can be a problem using the BOMEM instrument if proper precautions are not taken it was thought that measurements done at 6300 per cm would more easily result in satisfactory intercomparisons. Very recent measurements of the CO 3 <-- 0 band fine intensities confirms results reported here that the intensities listed in HITRAN (High Resolution Molecular Absorption Database) for this band are on the order of six to seven percent too low. All of the infrared intensities in the current HITRAN tabulation are based on the electric dipole moment function reported fifteen years ago. The latter in turn was partly based on intensities for the 3 <-- 0 band reported thirty years ago. We have, therefore, redetermined the electric dipole moment function of ground electronic state CO.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text C. Chackerian, R. J. Kshirsagar, L. P. Giver, and L. R. Brown, "Absolute Rovibrational Intensities for the X1Σ+v=3←0 Band of 12C16O Obtained with Kitt Peak and BOMEM FTS Instruments," in Fourier Transform Spectroscopy: New Methods and Applications, OSA Technical Digest (Optica Publishing Group, 1999), paper FWE22. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article