Absolute nu(2) Line Intensities of HOCl by Simultaneous Measurements in the Infrared with a Tunable Diode Laser and Far-Infrared Region Using a Fourier Transform Spectrometer

We have measured absolute line intensities in the nu(2) fundamental band at 1238 cm(-1) of both isotopomers of hypochlorous acid, HOCl. To obtain the partial pressure of the species in the sample mixture, unavailable through direct measurement since HOCl exists only in equilibrium with H(2)O and Cl(2)O and may decay by secondary reactions, we relied on known absolute line intensities in the pure rotational far-infrared (FIR) spectrum determined from Stark effect measurements. We have thus recorded simultaneously the FIR pure rotation spectrum of HOCl using a Bruker IFS120HR interferometer and the spectrum of a few vibration-rotation lines in the infrared (IR) nu(2) band using a tunable diode laser spectrometer. The absolute intensities of these IR lines thus determined allowed us to "calibrate" the intensities of vibration-rotation lines in the whole nu(2) band, measured previously using Fourier transform spectroscopy. The treatment of the data took into account the blackbody emission contribution in the FIR and the evolution of the HOCl amount during the recording of the spectra. The latter was found to be almost constant over hours after conditioning of the cell. The square of the nu(2) band vibrational transition dipole moment was determined to be 0.013947(23) D(2) and 0.013870(51) D(2) for HO(35)Cl and HO(37)Cl, respectively, that is, 29 to 73% lower than previous measurements. A linear Herman-Wallis factor was also determined for both isotopomers. Finally, the line intensities were least-squares fitted using a model that takes into account a weak resonance between the (010) and (002) levels. Copyright 2000 Academic Press.

New High-Resolution Analysis of the nu(3) Band of the (15)N(16)O(2) Isotopomer of Nitrogen Dioxide by Fourier Transform Spectroscopy

New high-resolution Fourier transform absorption spectra of an (15)N(16)O(2) isotopic sample of nitrogen dioxide were recorded at the University of Bremen in the 6.3-µm region. Starting from the results of a previous study [Y. Hamada, J. Mol. Struct. 242, 367-377 (1991)], a new and more extended analysis of the nu(3) band located at 1582.1039 cm(-1) has been performed. The spin-rotation energy levels were satisfactorily reproduced using a theoretical model which takes into account both the Coriolis interactions between the spin-rotation energy levels of the (001) vibrational state with those of the (020) and (100) states and the spin-rotation resonances within each of the NO(2) vibrational states. Precise vibrational energies and rotational, spin-rotation, and coupling constants were obtained in this way for the first triad of (15)N(16)O(2) interacting states {(020), (100), (001)}. Finally, a comprehensive list of line positions and line intensities of the {nu(1), 2nu(2), nu(3)} interacting bands of (15)N(16)O(2) was generated, using for the line intensities the transition moment operators which were obtained previously for the main isotopic species. Copyright 2000 Academic Press.

First High-Resolution Infrared Observation of the Symmetry-Forbidden nu(5) Band of (10)B(2)H(6)

Spectra of (10)B monoisotopic diborane, B(2)H(6), have been recorded at high resolution (2-3 x 10(-3) cm(-1)) by means of Fourier transform spectroscopy in the region 700-1300 cm(-1). A thorough analysis of the nu(18) a-type, nu(14) c-type, and nu(5) symmetry-forbidden band has been performed. Of particular interest are the results concerning the nu(5) symmetry-forbidden band, which is observed only because it borrows intensity through an a-type Coriolis interaction with the very strong nu(18) infrared band located approximately 350 cm(-1) higher in wavenumber. The nu(5) band has been observed around 833 cm(-1) and consists of a well-resolved Q branch accompanied by weaker P- and R-branch lines. Very anomalous line intensities are seen, with the low K(a) transitions being vanishingly weak, and Raman-like selection rules observed. The determination of the upper state Hamiltonian constants proved to be difficult since the corresponding energy levels of each of the bands are strongly perturbed by nearby dark states. To account for these strong localized resonances, it was necessary to introduce the relevant interacting terms in the Hamiltonian. As a result the upper state energy levels were calculated satisfactorily, and precise vibrational energies and rotational and coupling constants were determined. In particular the following band centers were derived: nu(0) (nu(5)) = 832.8496(70) cm(-1), nu(0) (nu(14)) = 977.57843(70) cm(-1), and nu(0) (nu(18)) = 1178.6346(40) cm(-1). (Type A standard uncertainties (1varsigma) are given in parentheses.) Copyright 2000 Academic Press.

First Observation of the nu(17)-nu(4) Difference Bands of Diborane (10)B(2)H(6) and (11)B(2)H(6)

An analysis of the nu(17)-nu(4) difference bands near 800 cm(-1) of two isotopic species, (10)B(2)H(6) and (11)B(2)H(6), of diborane has been carried out using infrared spectra recorded with a resolution of ca. 0.003 cm(-1). In addition, the nu(17) band of (10)B(2)H(6) has been recorded and assigned. Since this band in (11)B(2)H(6) had already been studied (R. L. Sams, T. A. Blake, S. W. Sharpe, J.-M. Flaud, and W. J. Lafferty, J. Mol. Spectrosc. 191, 331-342 (1998)), it was possible to derive precise energy levels and Hamiltonian constants for the 4(1) vibrational states of both isotopic species. Copyright 2000 Academic Press.

Evidence of Vibrational-Induced Rotational Axis Switching for HD(12)C(16)O: New High-Resolution Analysis of the nu(5) and nu(6) Bands and First Analysis of the nu(4) Band (10-µm Region)

Using new high-resolution Fourier transform spectra recorded in Giessen in the 8-12 µm region, a more extended analysis of the nu(5) and nu(6) bands and the first high-resolution study of the nu(4) band of HDCO were performed. As pointed out previously [M. Allegrini, J. W. C. Johns, and A. R. W. McKellar, Can. J. Phys. 56, 859-864 (1978)], the energy levels of the 5(1) and 6(1) states are strongly coupled by A- and B-type Coriolis interactions. On the other hand, it appeared that weaker resonances involving the energy levels of the 4(1) state with those of the 5(1) and 6(1) states also had to be accounted for. Consequently, the calculation of the energy levels was performed taking into account the Coriolis-type resonances linking the energy levels of the {6(1), 5(1), 4(1)} resonating states. Because of the unusually strong Coriolis interaction between nu(5) and nu(6), a nonclassical behavior of the rotational levels of the 5(1) and 6(1) states was observed and it was necessary to use a new Hamiltonian matrix which possesses, as usual, both A- and B-type Coriolis operators in the 5(1) if 6(1) and 6(1) if 4(1) off diagonal blocks but differs from the classical reduced Hamiltonian which is used commonly for planar C(s)-type molecules. More precisely, it proved necessary to include non-orthorhombic terms in the expansion of the rotational Hamiltonian of the 5(1) and 6(1) states. According to the considerations developed by Watson [J. K. G. Watson, in "Vibrational Spectra and Structure," (J. Durig, Ed.), Chap. 1, Elsevier, Amsterdam, 1977], these non-orthorhombic operators which are not symmetry forbidden are usually removed for semirigid C(s)-type molecules by rotational contact transformations. In the present study, the occurrence of terms in {J(x), J(z)} in the expansions of the rotational Hamiltonians for the 5(1) and 6(1) states indicates that the inertial system of HDCO differs for each of the three {6(1), 5(1), 4(1)} resonating states. Therefore, HDCO becomes a good example of vibrational-induced rotational axis switching (VIRAS) which was already suggested as the mechanism responsible for the enhanced densities of coupled states observed in 2-fluoroethanol [H. Li, S. Erza, and L. A. Philips, J. Chem. Phys. 97, 5956-5963 (1992)]. Copyright 2000 Academic Press.

High-Resolution Infrared Spectrum of the Ring-Puckering Band, nu(10), of Diborane

The spectrum of the nu(10) band of diborane, arising from the ring-puckering vibration, has been obtained with a spectral resolution of 0.0015 cm(-1) in the region 275-400 cm(-1). The spectrum of a sample enriched in (10)B was recorded as well as one with naturally abundant boron, i.e., 64% (11)B(2)H(6), 32% (10)B(11)BH(6), and 4% (10)B(2)H(6). This mode is the lowest vibrational level of the molecule and is unperturbed, allowing a complete assignment of not only the fundamental bands but also the 2nu(10)-nu(10) hot bands of all three boron isotopomers. The intensities of several hundred lines of the fundamental and hot bands of all isotopomers have been measured and vibrational transition moments have been obtained. Finally, it has been shown that the harmonic approximation does not apply for nu(10). Copyright 2000 Academic Press.

New High-Resolution Analysis of the 3nu(3) and 2nu(1) + nu(3) Bands of Nitrogen Dioxide (NO(2)) by Fourier Transform Spectroscopy

Using new high-resolution Fourier transform spectra recorded at the University of Denver in the 2-µm region, a new and more extended analysis of the 2nu(1) + nu(3) and 3nu(3) bands of nitrogen dioxide, located at 4179.9374 and 4754.2039 cm(-1), respectively, has been performed. The spin-rotation energy levels were satisfactorily reproduced using a theoretical model that takes into account both the Coriolis interactions between the spin-rotation energy levels of the (201) vibrational "bright" state with those of the (220) "dark" state. The interactions between the (003) bright state with the (022) dark state were similarly treated. The spin-rotation resonances within each of the NO(2) vibrational states were also taken into account. The precise vibrational energies and the rotational, spin-rotational, and coupling constants were obtained for the two dyads {(220), (201)} and {(022), (003)} of the (14)N(16)O(2) interacting states. From the experimental line intensities of the 2nu(1) + nu(3) and 3nu(3) bands, a determination of their vibrational transition moment constants was performed. A comprehensive list of line positions and line intensities of the {2nu(1) + 2nu(2), 2nu(1) + nu(3)} and the {2nu(2) + 2nu(3), 3nu(3)} interacting bands of (14)N(16)O(2) was generated. In addition, assuming the harmonic approximation and using the Hamiltonian constants derived in this work and in previous studies (A. Perrin, J.-M. Flaud, A. Goldman, C. Camy-Peyret, W. J. Lafferty, Ph. Arcas, and C. P. Rinsland, J. Quant. Spectrosc. Radiat. Transfer 60, 839-850 (1998)), we have generated synthetic spectra for the {(022), (003)}-{(040), (021), (002)} hot bands at 6.3 µm and for the {(220), (201)}-{(100), (020), (001)} hot bands at 3.5 µm, which are in good agreement with the observed spectra. Copyright 2000 Academic Press.

The nu(1) and nu(3) Bands of the (17)O(16)O(17)O Isotopomer of Ozone

Using 0.002 cm(-1) resolution Fourier transform absorption spectra of an (17)O-enriched ozone sample, an extensive analysis of the nu(3) band together with a partial identification of the nu(1) band of the (17)O(16)O(17)O isotopomer of ozone has been performed for the first time. As for other C(2v)-type ozone isotopomers [J.-M. Flaud and R. Bacis, Spectrochim. Acta, Part A 54, 3-16 (1998)], the (001) rotational levels are involved in a Coriolis-type resonance with the levels of the (100) vibrational state. The experimental rotational levels of the (001) and (100) vibrational states have been satisfactorily reproduced using a Hamiltonian matrix which takes into account the observed rovibrational resonances. In this way precise vibrational energies and rotational and coupling constants were deduced and the following band centers nu(0)(nu(3)) = 1030.0946 cm(-1) and nu(0)(nu(1)) = 1086.7490 cm(-1) were obtained for the nu(3) and nu(1) bands, respectively. Copyright 2000 Academic Press.

The nu(2) Bands of the Deuterated Species D(2)Se and HDSe

For the first time D(2)Se and HDSe as (80)Se monoisotopic and natural material were studied in the region of the nu(2) fundamental vibration by high-resolution (0.0033 cm(-1)) Fourier transform infrared spectroscopy. For D(2)Se which is an asymmetric rotor with C(2v) symmetry the nu(2) band is of B type while for HDSe (C(s) symmetry) it is a hybrid band, and both A- and B-type transitions were observed. Depending on the isotopic abundances, 300-1000 lines were assigned for each of the isotopic (M)Se species (M = 76, 77, 78, 80, and 82). The corresponding (010) experimental rotational levels, obtained by adding the observed line positions to the ground state levels derived from J.-M. Flaud, Ph. Arcas, O. N. Ulenikov, G. A. Onopenko, N. E. Tyabaeva, W. Jerzembeck, and H. Bürger, (J. Mol. Spectrosc., in press) were fitted satisfactorily using a Watson-type Hamiltonian in A reduction and I(r)-representation: the rms deviations are ranging from 1.5 to 4.3 x 10(-4) cm(-1) depending on the isotopic species. Hamiltonian constants up to high order (octic terms) were determined for each isotopic species. For the most abundant Se isotopic species, namely (80)Se, the band centers are nu(0) (D(2)(80)Se) = 741.67503 cm(-1) and nu(0) (HD(80)Se) = 900.43820 cm(-1). Copyright 1999 Academic Press.

The Ground State of D(2)Se and HDSe

Ground state rotational constants of D(M)(2)Se and HD(M)Se, M = 76, 77, 78, 80, and 82, have been determined up to octic centrifugal distortion terms from ground state combination differences. These were obtained from rotational analyses of the nu(2), nu(1), and nu(3) bands both of natural and (80)Se monoisotopic material recorded with a resolution of ca. 3 x 10(-3) cm(-1). While the full set of rotational parameters of the (80)Se species was determined with significance, some of the centrifugal distortion terms of the less abundant species were either constrained to those of the (80)Se species or extrapolated. Copyright 1999 Academic Press.

Absolute Line Intensities for the nu6 Band of H2O2

The purpose of this work was to obtain reliable absolute intensities for the nu6 band of H2O2. It was undertaken because strong discrepancies exist between the different nu6 band intensities which are presently available in the literature (A. Perrin, A. Valentin, J.-M. Flaud, C. Camy-Peyret, L. Schriver, A. Schriver, and P. Arcas, J. Mol. Spectrosc. 1995. 171, 358), (R. May, J. Quant. Radiat. Transfer 1991. 45, 267), and (R. L. Sams, personal communication). The method which was chosen in the present work was to measure simultaneously the far-infrared absorptions and the nu6 absorptions of H2O2. Consequently, Fourier transform spectra of H2O2 were recorded at Giessen in a spectral range (370-1270 cm-1) which covers both the R branch of the torsion-rotation band and the P branch of the nu6 band which appear at low and high wavenumbers, respectively. From the low wavenumber data, the partial pressure of H2O2 present in the cell during the recording of the spectra was determined by calibrating the observed absorptions in the torsion-rotation band with intensities computed using the permanent H2O2 dipole moment measured by Stark effect (A. Perrin, J.-M. Flaud, C. Camy-Peyret, R. Schermaul, M. Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, and J. Koput, J. Mol. Spectrosc. 1996. 176, 287-296) and [E. A. Cohen and H. M. Pickett, J. Mol. Spectrosc. 1981. 87, 582-583). In the high frequency range, this value of the partial pressure of H2O2 was used to measure absolute line intensities in the nu6 band. Finally, the line intensities in the nu6 band were fitted using the theoretical methods described in detail in our previous works. Using these new results on line intensities together with the line position parameters that we obtained previously, a new synthetic spectra of the nu6 band was generated, leading to a total band intensity of 0.185 x 10(-16) cm-1/(molecule.cm-2) at 296 K. It has to be pointed out that the new line intensities agree to within the experimental uncertainties with the individual line intensity measurements performed previously by May and by Sams. Copyright 1999 Academic Press.

The High-Resolution Raman Spectrum of the nu4 Band of Diborane

The high-resolution Raman spectra of the nu4 bands of 11B2H6 and 11B10BH6 have been recorded and analyzed. The recordings have been made using a high-resolution spectrometer based on the inverse Raman effect. Q branches have been observed, but P and R branches were too weak to be seen, and simulations of the observed band contour have been necessary to complete the analysis. A weak Coriolis resonance with the 2nu10 level is present in the 11B2H6 spectrum. The band centers obtained are 790.9829(12) and 804.76985(27) cm-1 for 11B2H6 and 10B11BH6, respectively (uncertainties are type A with a coverage factor k = 1, i.e., 1 standard deviation). Copyright 1999 Academic Press.

Analysis of the nu8 + nu9 Band of HNO3, Line Positions and Intensities, and Resonances Involving the v6 = v7 = 1 Dark State

Using a high-resolution (R = 0.0025 cm-1) Fourier transform spectrum of nitric acid recorded at room temperature in the 1100-1240 cm-1 region, it has been possible to perform a more extended analysis of the nu8 + nu9 band of HNO3 centered at 1205.7075 cm-1. As in a recent analysis of this band [W. F. Wang, P. P. Ong, T. L. Tan, E. C. Looi, and H. H. Teo, J. Mol. Spectrosc. 183, 407-413 (1997)], the Hamiltonian used for the line positions calculation takes into account, for the upper state, the DeltaK = +/-2 anharmonic resonance linking the rotational levels of the v8 = v9 = 1 "bright" vibrational state and those of the "dark" v6 = v7 = 1 vibrational state. More than 4800 lines were assigned in the nu8 + nu9 band, which involve significantly higher rotational quantum numbers than in previous works. On the other hand, and surprisingly as compared to previous studies, the nu8 + nu9 band appears to be a hybrid band. In fact, nonnegligible B-type transitions could be clearly identified among the much stronger A-type lines. Accordingly, a set of individual line intensities were measured for lines of both types and were introduced in a least-squares fit to get the A- and B-type components of the transition moment operator. Finally, a synthetic spectrum of the 8.3-µm region of HNO3 has been generated, using for the line positions and line intensities the Hamiltonian constants and the expansion of the transition moment operator which were determined in this work. In this way, the B-type and the A-type components of the nu8 + nu9 band appear to contribute for about (1/4) and (3/4), respectively, to the total band intensity. Copyright 1999 Academic Press.

The Far Infrared Spectrum of HOCl: Line Positions and Intensities

The far infrared spectrum of HOCl has been recorded at high resolution between 20 and 360 cm-1 by means of Fourier transform spectroscopy, and it was possible to observe pure rotation lines involving rotational levels with high Ka quantum numbers (up to Ka = 9). These lines combined with microwave and tunable far infrared data available in the literature were least squares fitted using a Watson-type Hamiltonian. The fitting leads to precise sets of rotational and centrifugal distortion constants for the ground states of both isotopomers HO35Cl and HO37Cl. Also relative line intensities were measured and their fitting allowed the determination of rotational corrections to the b-component of the permanent transition moment. Finally, to get Hamiltonian constants consistent with the newly determined ground state constants for the (100), (010), (001) vibrational states, available data concerning the nu1, nu2, and nu3 bands were refitted. Three interesting points are to be stressed. For the (001) state, we were able to complete the existing data with rotation lines observed in our spectra up to rather high Ka values (Ka = 7). For HO35Cl, we were able to show that some (010) and (100) levels are perturbed by levels of the (002) and (030) states, respectively, through Coriolis-type interactions. This allows the determination of the band centers of these two dark states. Copyright 1998 Academic Press.

High-Resolution Infrared Study of the nu14, nu17, and nu18 Bands of 11B2H6 and 10B11BH6

Using high-resolution Fourier transform spectra, a thorough analysis of the nu14 c-type, nu17 a-type, and nu18 a-type bands of both 11B2H6 and 10B11BH6 has been carried in the 10.3-, 6.2-, and 8.5-µm spectral regions, respectively. From this analysis a large set of precise ground state combination differences with J values up to 36 (31) and Ka values extending to 18 (18) was derived for 11B2H6(10B11BH6). These data were fitted using a Watson-type Hamiltonian leading to accurate ground state rotational constants. An rs value for the B-B distance has been determined to be 1.7645(10) Å. The determination of upper state Hamiltonian constants proved to be much more difficult since the corresponding rotational levels of each of the bands are strongly perturbed by nearby dark states. To account for these strong localized resonances, it was necessary to introduce the relevant interacting terms in the Hamiltonian matrix. As a result it was possible to calculate the upper state energy levels quite satisfactorily. From these fits, estimates of the band centers and a few of the rotational constants of the resonating dark states were obtained. Copyright 1998 Academic Press.

High-Resolution Analysis of the nu6, nu7, nu8, and nu9 Bands of H15N16O3 Measured by Fourier Transform Spectroscopy

The analysis of the nu6, nu7, nu8, and nu9 bands of H15N16O3 located at 646.9641, 578.4719, 743.6166, and 458.2917 cm-1, respectively, has been carried out in the 400-800 cm-1 region using high-resolution Fourier transform spectra recorded at Ottawa. Using the ground state energy levels calculated from the v = 0 rotational constants of H15N16O3 [A. P. Cox, M. C. Ellis, C. J. Attfield, and A. C. Ferris, J. Mol. Struct. 320, 91-106 (1994)], it was possible to assign the A-type nu6 and nu7 bands and the C-type nu8 and nu9 bands of H15N16O3 up to high J and Ka rotational quantum numbers. The v6 = 1, v7 = 1, v8 = 1, and v9 = 1 experimental energy levels were then introduced in a least-squares fit calculation and precise upper state Hamiltonian constants (band centers and rotational constants) were determined allowing one to reproduce the infrared data to within the experimental uncertainty. Copyright 1998 Academic Press.

High Frequency Transitions in the Rotational Spectrum of SO2

A large number of rotational transitions of 32S16O2, 34S16O2, and 32S18O16O have been measured in the mm-, submm-, and terahertz ( approximately 1 THz) spectral regions. These data sets have been combined with all previously measured SO2 microwave and selected far infrared data to obtain a highly precise set of ground state rotational constants for these isotopomers. The rotational constants for the three isotopomers are in MHz as follows: Parameter32S16O234S16O232S18O16O A60778.54977 (44)58991.18295 (51)59101.1690 (27) B10318.07348 (7)10318.50993 (9)9724.64284 (56) C8799.703399 (70)8761.302481 (97)8331.56018 (51) Centrifugal distortion constants up to P10 are included in the fit. A frequency listing of all the data used in the frequency range between about 7 GHz and 1 THz is included. Copyright 1998 Academic Press.

The H2S Spectrum around 0.7 µm

The overtone spectrum of H2S has been recorded by intracavity laser spectroscopy in the 14100-14400 cm-1 spectral region. The rovibrational analysis was performed allowing one to assign not only lines involving the pair of interacting states {(402), (303)} ({(60(+), 0), (60(-), 0)} in local mode notation), but also lines involving the interacting states {(322), (223)} ({50(+), 2), (50(-), 2)} in local mode notation). Indeed, apart from the strong H22 interactions that link the rotational levels of the states (60(+/-), 0) on the one hand, and the rotational levels of the states (50(+), 2) on the other hand, we observe that the rotational levels of the two pairs of states interact strongly through anharmonic and Coriolis-type resonances. These resonances transfer intensity to lines involving the (50(+), 2) pair of states. Altogether 80 rotational upper-state levels have been observed and reproduced satisfactorily using an Hamiltonian matrix that takes explicitly into account the various interactions and assumes the same vibrational energy and rotational constants for the two components of the local mode pairs. The following band centers have been obtained: nu0 (60(+), 0) = 14291.122 cm-1 and nu0 (50(+/-), 2) = 14284.705 cm-1. Finally a local mode-type behavior is evidenced by the values of the Hamiltonian constants, and refined vibrational local mode parameters are obtained. Copyright 1998 Academic Press.

Line Intensities for the 8-µm Bands of SO2

Using both high-resolution (R = 0.003 cm-1) and medium-resolution (R = 0.12 cm-1) Fourier transform spectroscopy, it has been possible to measure accurately a large set of individual line intensities for the nu1 and nu3 bands of SO2 in the 950-1400 cm-1 spectral region. These intensities were introduced into a least-squares fit calculation allowing one to obtain the expansion of the transition moment operator of the nu1 and nu3 bands. For these intensity calculations, the theoretical model takes into account the vibration-rotation interactions linking the upper levels involved in the nu1, 2nu2, and nu3 interacting SO2 bands. Finally, a synthetic spectrum of the 8-µm SO2 bands has been generated using the dipole moment expansion determined in this work and the molecular parameters and the Hamiltonian matrix given in a previous analysis. Copyright 1998 Academic Press.

New High-Resolution Analysis of the nu3, nu4, and nu6 Bands of D2CO Measured by Fourier Transform Spectroscopy

A reanalysis of the nu3, nu4, and nu6 interacting bands of D2CO has been carried out in the region 850-1250 cm-1 using high-resolution Fourier transform spectra recorded at Giessen. As compared to the previous study of these bands (1987, K. Nakagawa, R. H. Schwendeman, and J. W. C. Johns, J. Mol. Spectrosc. 122, 462-476) higher J and Ka transitions were assigned for the three bands, leading to a better determination of the upper state constants. The v3 = 1, v4 = 1, and v6 = 1 experimental energy levels were introduced in a least-squares fit calculation together with the microwave measurements available in the literature in order to obtain the upper state parameters (band centers, rotational and coupling constants). In this calculation, which allowed us to reproduce both the infrared and the microwave measurements to within their experimental accuracies, the A-, B-, and C-type Coriolis interactions involving the rotational levels belonging to the v4 = 1 and v6 = 1, v3 = 1 and v4 = 1, and v3 = 1 and v6 = 1 interacting states respectively were explicitly taken into account. Finally, from the intensities, a new determination of the relative values of the q3, q4, and q6 first derivatives of the D2CO dipole moment was performed. Copyright 1998 Academic Press. Copyright 1998Academic Press

The Water Vapor Linestrengths between 11 600 and 12 750 cm-1

The water vapor linestrengths in the region of the 3nu + delta resonance polyad of interacting vibrational states (the corresponding upper states are (310), (211), (112), (013), (131), (230), (032), and (051)) have been analyzed leading to accurate dipole moment transition parameters. The effective rotational Hamiltonian constants used to calculate the vibration-rotation wavefunctions (J.-M. Flaud, C. Camy-Peyret, A. Bykov, O. Naumenko, T. Petrova, A. Scherbakov, L. Sinitsa, 1994. J. Mol. Spectrosc. 183, 300-309) take into account both strong centrifugal distortion effects and dark states presence. These effects are known to be important for the highly excited vibrational states of water-like molecules. The input data set included the line intensities measured by Toth (R. Toth, 1994. J. Mol. Spectrosc. 166, 176-183) and the line intensities of the weak bands 2nu1 + 3nu2, 3nu2 + 2nu3, and 3nu1 + nu2 derived from peak absorptions of a spectrum recorded at a pressure of 17.0 Torr and a path length of 434 m. The parameters of the effective dipole moment operator determined by least square fitting give a very satisfactory agreement with experimental values since the mean error for the 876 experimental linestrengths is only 3.9%. It is worth noticing that such an agreement could be reached only because high-order resonance couplings with dark states were explicitly taken into account. Copyright 1997 Academic Press. Copyright 1997Academic Press

The High-Resolution Spectrum of Water Vapor between 11 600 and 12 750 cm-1

The absorption spectrum of water vapor has been recorded between 11 600 and 12 750 cm-1 with a Fourier transform spectrometer (Kitt Peak, Az) at a resolution of 0.012 cm-1 and with a path length of 434 m. The line assignment has led to the determination of 506 accurate energy levels of the (310) (211), (112), (013), (230), (131), (032), and (051) vibrational states which belong to the so-called 3nu + delta resonance polyad. The rotational energy levels obtained are on the average in agreement with those reported recently by R. Toth (J. Mol. Spectrosc. 166, 176-183 (1994)) for the strong bands, but there are differences for high J levels or weak bands levels (about 15% of all levels). The experimental rotational energy levels have been fitted using Pade-Borel approximants and a set of 104 vibrational energies and rotational, resonance, and centrifugal distortion constants for the (310), (211), (112), (013), (230), (131), (032), and (051) vibrational states have been determined.

Infrared Diode-Laser Molecular-Beam Spectrum of the nu2 Band of Chlorine Nitrate at 1293 cm-1

The nu2 band of chlorine nitrate (ClONO2 ) near 1293 cm-1 has been measured in a molecular beam with a diode-laser spectrometer. The low rotational temperature of the molecular beam, approximately 23 K, simplifies the spectrum allowing essentially complete assignment of the 35 Cl and 37 Cl lines. An a /b hybrid band is observed with the a -type transition moment being approximately a factor of 2 larger than the b -type transition moment. An inverted shift of the band origins is found with the 37 Cl band origin blue shifted from the 35 Cl by +0.37 cm-1 . This isotopic shift is attributed to an unidentified anharmonic resonance. Precise spectroscopic constants for the bands of each isotopic species are determined to allow future simulations for modeling atmospheric transmission and for remote sensing applications.

High Resolution Study of the 3nu2, nu1 + nu2, and nu2 + nu3 Bands of H2Te

High-resolution Fourier transform spectra of a natural sample of hydrogen telluride and of monoisotopic H2130Te have been recorded in the 3.2-4-0 μm spectral region where the 3nu2, nu1 + nu2, and nu2 + nu3 bands of this molecule absorb. The (030) rotational levels were least-squares fitted using a Watson-type Hamiltonian whereas it proved necessary to consider the strong Coriolis interaction coupling the (110) and the (011) rotational levels. In this way all the experimental levels were calculated to within their experimental uncertainty and precise sets of vibrational energies and rotational and coupling constants were obtained for the (030), (110), and (011) vibrational states of H2130Te, H2128Te, H2126Te, H2125Te, H2124Te, H2123Te, and H2122Te. The band centers for the most abundant isotopic species, namely H2130Te, are:nuo(3nu2) = 2565.4428, nuo(nu1 + nu2) = 2911.4098, nuo(nu2 + nu3) = 2915.9599 cm-1 Copyright 1997Academic Press

Simultaneous Analysis of the 2nu2, nu1, and nu3 Bands of Hydrogen Telluride

Spectra of a natural sample of hydrogen telluride as well as a spectrum of monoisotopic H2 130Te have been recorded by means of Fourier transform spectrometry with a resolution of 0.003 cm-1 in the spectral domain 7.5-4.3 μm where it is easy to observe the main absorbing bands nu1 and nu3. We have located and assigned for the first time the 2nu2 band which appears in the lower wavenumber range of the recorded spectral domain near 1700 cm-1. It proved necessary to treat simultaneously the three states (020), (100), and (001). nu1 and nu3 are indeed Coriolis-coupled vibration-rotation bands and it was observed that a few rotational levels of (001) could not be fitted to within their experimental accuracy without considering the second-order Coriolis interaction between the rotational levels of (020) and (001). In this way all the experimental levels were calculated to within the experimental uncertainty, and precise sets of vibrational energies and rotational and coupling constants were obtained for the seven most abundant H2Te isotopic species, namely H2 130Te, H2 128Te, H2 126Te, H2 125Te, H2 124Te, H2 123Te, and H2 122Te. For the most abundant isotopic species H2 130Te the bands centers arenu0 (2nu2) = 1715.9568, nu0 (nu1) = 2065.2709, nu0 (nu3) = 2072.1101 cm-1. Copyright 1997Academic Press