New laboratory intercomparison of the ozone absorption coefficients in the mid-infrared (10 µm) and ultraviolet (300-350 nm) spectral regions.

Knowing the ozone absorption cross sections in the ultraviolet and infrared spectral range, with an accuracy of better than 1%, is of the utmost importance for atmospheric remote-sensing applications. For this reason, various ozone intensity intercomparisons and measurements have been published these last years. However, the corresponding results proved not to be consistent and thus have raised a controversial discussion in the community of atmospheric remote-sensing. This study, where great care has been taken to avoid any possible error, reports a new laboratory intercomparison of the ozone absorption coefficients in the mid-infrared (10 µm) and ultraviolet (300-350 nm) spectral regions. It gives a new piece of information to the puzzling problem concerning the ozone IR and UV cross sections and confirms that the IR and UV cross sections recommended in the literature are in disagreement of about 4%.

Laboratory intercomparison of the ozone absorption coefficients in the mid-infrared (10 microm) and ultraviolet (300-350 nm) spectral regions.

For the measurement of atmospheric ozone concentrations, the mid-infrared and ultraviolet regions are both used by ground-, air-, or satellite-borne instruments. In this study we report the first laboratory intercomparison of the ozone absorption coefficients using simultaneous measurements in these spectral regions. The intercomparison shows good agreement (around 98.5%) between the HITRAN 2000 recommendation for the mid-infrared and the most reference measurements in the ultraviolet regions, whereas systematic differences of about 5.5% are observed when using the recommendation of HITRAN2003 for the mid-infrared. Possible reasons for this discrepancy are discussed. Future measurements are clearly needed to resolve this issue.

High-Resolution Infrared, Microwave, and Submillimeter-Wave Study of FClO(2) in the nu(2), nu(3), nu(4), and nu(6) Excited States.

A high-resolution analysis of the {nu(2), nu(3)} and {nu(4), nu(6)} bands of the two isotopomers of chloryl fluoride F(35)ClO(2) and F(37)ClO(2) has been carried out for the first time using simultaneously infrared spectra recorded around 16&mgr;m and 26&mgr;m with a resolution of ca. 0.003 cm(-1) and microwave and submillimeter-wave transitions occurring within the vibrational states 2(1), 3(1), 4(1), and 6(1). Taking into account the Coriolis resonances which link the rotational levels of the {2(1), 3(1)} and the {4(1), 6(1)} interacting states, it was possible to reproduce very satisfactorily the observed transitions and to determine accurate vibrational energies and rotational constants for the upper states 2(1), 3(1), 4(1), and 6(1) of both the (35)Cl and (37)Cl isotopic species. Copyright 2001 Academic Press.

The v(1)+v(3) Bands of the (16)O(17)O(16)O and (16)O(16)O(17)O Isotopomers of Ozone.

Using 0.002 cm(-1) resolution Fourier transform absorption spectra of an (17)O enriched ozone sample, an extensive analysis of the v(1)+v(3) bands of the (16)O(17)O(16)O and (16)O(16)O(17)O isotopomers of ozone has been performed for the first time. The experimental rotational levels of the (101) vibrational states were satisfactorily reproduced using a Hamiltonian matrix that takes into account the observed rovibrational resonances. More precisely, for (16)O(17)O(16)O, as for the other C(2v)-type ozone isotopomers, it was necessary to account for the Coriolis type resonances linking the (101) rotational levels with the levels of the (200) and (002) vibrational states and the Darling-Dennison interaction coupling the levels of (200) with those of (002). For the C(s)-type isotopomer, namely (16)O(16)O(17)O, as for (16)O(16)O(18)O and (16)O(18)O(18)O, it proved necessary to also account for an additional DeltaK(a)&equals+/-2 resonance involving the rotational levels from (101) and (002) (J.-M. Flaud and R. Bacis, Spectrochimica Acta Part A 54, 3-16 (1998)). Using a Hamiltonian matrix which takes these resonances explicitly into account, precise vibrational energies and rotational and coupling constants were deduced, leading to the following band centers: v(0)(v(1)+v(3))=2078.3496 cm(-1) for (16)O(17)O(16)O and v(0)(v(1)+v(3))=2098.8631 cm(-1) for (16)O(16)O(17)O. Copyright 2001 Academic Press.

Absolute Intensities of the nu(1) and nu(3) Bands of (16)O(3).

New experimental data on the nu(1) and nu(3) bands of (16)O(3) improving the value of absolute line intensities have been obtained. The intensities of 295 lines have been measured with an average accuracy between 2.5% and 3% and the rotational expansion of the transition moment operators for the nu(1) and nu(3) bands has been deduced. Finally, a complete listing of line intensities has been computed with an intensity cutoff of 1x10(-25) cm(-1)/molecule cm(-2). 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.

High-Resolution IR Spectrum of SCF(2) from 1000 to 1400 cm(-1): The nu(1)/nu(3) + 2nu(5)/nu(2) + nu(3) and nu(4)/nu(2) + nu(5) Interacting States.

The infrared spectrum of SCF(2) was recorded in the 1000-1400 cm(-1) region with a resolution of 2.5 x 10(-3) cm(-1). The rotationally resolved nu(1) and nu(4) band systems were studied for the first time, and altogether 11 500 transitions were assigned. Both fundamentals are involved in strong anharmonic (Fermi) resonances. Effective centers (J = K(a) = K(c) = 0) of the interacting bands are nu(1) 1366.7117 cm(-1), nu(3) + 2nu(5) 1365.4257 cm(-1), nu(2) + nu(3) 1311.1491 cm(-1) (a(1) species), and nu(4) 1190.0839 cm(-1), nu(2) + nu(5) 1217.8191 cm(-1) (b(1) species). The strong K(a) dependence of the nu(1)/nu(3) + 2nu(5) level mixing enabled a numerical determination of the interaction constants while the other anharmonic interactions were accounted for by consideration of relative intensities. Deperturbed band centers, anharmonicity constants, and equilibrium and excited state rotational and centrifugal distortion constants were determined. Copyright 1999 Academic Press.

The Overtone Spectrum of H2 32S near 13 200 cm-1.

The intracavity laser absorption spectrum of H2 32S has been recorded near 13 200 cm-1 with an equivalent absorption pathlength of 25 km. The observed spectrum is assigned to the (50(+/-), v2 = 1) states constituting a local mode pair in strong H22-type interaction. The rovibrational analysis has allowed the assignment of 210 lines involving 86 rotational upper state levels which have been reproduced with a rms of 0.023 cm-1 close to the experimental accuracy. A perturbation affecting one line is assigned to a local interaction with the (40(+/-), v2 = 3) local mode pair. The influence of the bending excitation on the local mode character of the (n0(+/-), v2 = 1) stretch-bend combination levels is discussed on the basis of the values of the rotational constants and of the H22 interaction parameters. Copyright 1999 Academic Press.

High Resolution Study of the nu2 , 2nu1 , nu1 + nu3 , and 2nu3 Bands of Hydrogen Telluride: Determination of Equilibrium Rotational Constants and Structure

High resolution Fourier transform spectra of a natural and a 130 Te monoisotopic sample of H2 Te have been recorded at a resolution of 0.0022 cm-1 in the 11.6 µm spectral region, as well as a spectrum of a natural sample of H2 Te at a resolution of 0.0051 cm-1 in the 2.4 µm region. In the 11.6 µm region the main absorbing band is the nu2 band, the analysis of which was rather easy. On the other hand, in the 2.4 µm region three bands are absorbing, namely 2nu1 , nu1 + nu3 , and 2nu3 , the last being much weaker than the others. The analysis in this spectral domain was much more difficult because of resonances. Indeed it proved not possible to reproduce the observed lines without taking into account the Darling-Dennison interaction between the levels of the (200) and (002) states and the Coriolis interactions between the levels of (200) and (101) and between those of (101) and (002). Considering these interactions allowed us to calculate very satisfactorily all the experimental levels, and precise sets of vibrational energies and rotational and coupling constants were obtained for the seven most abundant H2 Te isotopic species, namely H2 130 Te, H2 128 Te, H2 126 Te, H2 125 Te, H2 124 Te, H2 123 Te, and H2 122 Te. For the most abundant species, H2 130 Te, the band centers in cm-1 are nu0 (nu2 ) = 860.6563, nu0 (2nu1 ) = 4062.8842, nu0 (nu1 + nu3 ) = 4063.3697, and nu0 (2nu3 ) = 4137.0454. These results, combined with those obtained for other vibrational states, have been used to derive the equilibrium rotational constants and their corrections. Finally, by neglecting the electronic corrections, the equilibrium structure of H2 130 Te was obtained as follows: r e (Te-H) = 1.65145(10) A, alphae (HTeH) = 90.2635(90)degrees.