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  • 1
    Electronic Resource
    Electronic Resource
    Line mixing in the ν1 and 2ν2 isotropic Raman Q-branch of CO2 perturbed by argon and helium (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 9315-9324 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The shapes of the ν1 and 2ν2 isotropic Raman Q-branch of CO2 perturbed by argon and helium have been measured by Stimulated Raman Spectroscopy (SRS) or coherent anti-Stokes Raman Spectroscopy (CARS) techniques. The data have been successfully analyzed with an energy corrected sudden (ECS) approximation model based on basic rates determined independently. Finally comparison of the present data with time resolved double resonance experiments allows us to discuss the physical origin of the two empirical constants which account for the shift and broadening of the branch due to vibrational effects. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480031
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  • 2
    Electronic Resource
    Electronic Resource
    Collision-induced double transition effects in the 3ν3 CO2 band wing region (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 2067-2072 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: IR absorption beyond the head of the 0003–0000 (3ν3) band of CO2 near 7000 cm−1 has been analyzed. This absorption is found to consist of two comparable intensity contributions, namely, the allowed band wing and a collision-induced absorption (CIA) band. The band wing profile has been described by using a non-Markovian theory and the rotational perturbation densities for CO2–CO2 collisions, which was previously calculated from the intensity distribution in the high-frequency wing of the 0001–0000 CO2 band. The CIA component has a typical shape of CO2 CIA bands with the maximum at the double transition (0001+0002)–(0000+0000) frequency. The integrated binary coefficient of this CIA band was estimated to be B2=(1.0±0.6)×10−5 cm−2 Amagat−2. The CIA spectral moment theory has been used for the intensity calculation, which takes into account for the first time the collision-induced vibrational force field in CO2 pairs. By comparing the calculated and measured intensity for the double transition, the polarizability anisotropy matrix element for the 2ν3 band has been estimated as β20=0.26±0.08 a.u., value in reasonable agreement with an independent estimation from previous results of polarizability matrix elements of CO2. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473140
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  • 3
    Electronic Resource
    Electronic Resource
    Line-mixing effects in N2O Q branches: Model, laboratory, and atmospheric spectra (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 1959-1968 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A model based on the energy corrected sudden approximation is used in order to account for line-mixing effects in N2O Q branches of Σ↔Π bands. The performance of this theoretical approach is demonstrated by comparisons with many (about 70) N2O–N2 and N2O–O2 laboratory spectra recorded in the 5 and 17 μm regions by three instrument setups; the Q branches of the 2ν20e–ν21f (near 579.3 cm−1), ν2 (near 588.8 cm−1), and ν2+ν3 (near 2798.3 cm−1) bands are investigated for different pressures (0.1–2.0 atm) and temperatures (200–300 K). The model is used to generate a set of line-mixing parameters for the calculation of the absorption by the ν2 Q branch under atmospheric conditions. These data are tested by comparisons between computed stratospheric emissions and values measured using a balloon-borne high resolution Fourier transform instrument. The results confirm the need to account for the effects of line mixing and demonstrate the capability of the model to represent the N2O absorption in a region which can be used for the retrieval of N2O5 mixing ratios. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477862
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  • 4
    Electronic Resource
    Electronic Resource
    Collision-induced absorption by H2 pairs in the second overtone band at 298 and 77.5 K: Comparison between experimental and theoretical results (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 4750-4756 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The collision-induced spectra of hydrogen in the region of the second overtone at 0.8 μm have been recorded at temperatures of 298 and 77.5 K and for gas densities ranging from 100 to 800 amagats. The spectral profile defined by the absorption coefficient per squared density varies significantly with the density, so that the binary absorption coefficient has been determined by extrapolations to zero density of the measured profiles. Our extrapolated measurements and our recent ab initio quantum calculation are in relatively good agreement with one another. Taking into account the very weak absorption of the second overtone band, the agreement is, however, not as good as it has become (our) standard for strong bands. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477813
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  • 5
    Electronic Resource
    Electronic Resource
    Line-mixing effects in He- and N2-broadened Σ↔Π infrared Q branches of N2O (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6684-6690 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Two Q branches of N2O near 579.3 and 2798 cm−1 belonging to the 2ν20e−ν21f and ν2+ν3 bands, respectively, of Σ←Π and Π←Σ symmetry, have been studied for He and N2 perturbers at pressures ranging from 0.1 to 2 atm, using a tunable diode laser and a difference-frequency laser spectrometer. To interpret the line-mixing effects in these spectra, we have applied a model based on the energy corrected sudden approximation whose parameters have been only derived from line-broadening data for N2O–He and also from the measured absorption by the Q branches for N2O–N2. This model provides a satisfactory agreement with experimental band shapes, whatever the band, the perturber and the pressure considered. Significantly larger line-mixing effects are shown for N2O–He with respect to N2O–N2. Finally, the assumption made in the calculations to treat separately the couplings in the even and odd j levels appears to have a negligible influence on the resulting band shapes. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477318
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure induced shifts of CO2 lines: Measurements in the 0003–0000 band and theoretical analysis (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4945-4953 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Self-broadened and N2, Ar, He-broadened halfwidth and pressure shift coefficients of the rotational transitions in the 0003–0000 band of 12C16O2 have been measured from laboratory absorption recorded at room temperature with a Fourier transform spectrometer. Comparison is made with the results of a theoretical calculation based on a semiclassical model. Good agreement is obtained for all the IR vibrational bands for which data are available. It has been shown that the shifts mainly originate from vibrational dephasing. Infrared line shifts have been compared with results obtained from stimulated Raman spectroscopy and we show that they are not consistent. A number of possible explanations have been discussed to account for this discrepancy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462737
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  • 7
    Electronic Resource
    Electronic Resource
    Line-mixing effects in Ar-broadened doublets of a hot band of OCS (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6962-6970 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The spectra of several Ar-broadened symmetric doublets in the hot band ν1+ν2−ν2 (at 850 cm−1) of OC 32S have been recorded with a tunable diode-laser spectrometer. The pressure-broadening coefficients measured for sufficiently separated lines belonging to 7 doublets are in agreement with the results previously obtained in the ν1 band. From these data, we have determined, for different pressures of argon, line-coupling coefficients for 15 doublets in the P and R branches of the hot band. These coefficients appear to be small and negative, at the limit of our estimated accuracy, which implies very weak line-mixing effects in the doublets, in agreement with the results of a semiclassical calculation as well as with results of coupling cross sections estimated at large-j values from the infinite order sudden (IOS) approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459682
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  • 8
    Electronic Resource
    Electronic Resource
    Line mixing and nonlinear density effects in the ν3 and 3ν3 infrared bands of CO2 perturbed by He up to 1000 bar (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 7306-7316 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present high density experimental and theoretical results on CO2–He absorption in the ν3 and 3ν3 infrared bands. Measurements have been made at room temperature for pressures up to 1000 bar in both the central and wing regions of the bands. Computations are based on an impact line-mixing approach in which the relaxation operator is modeled with the energy corrected sudden (ECS) approximation. Comparisons between experimental and calculated results demonstrate the accuracy of the ECS approach when applied to band wings and band centers at moderate densities. On the other hand, small but significant discrepancies appear at very high pressures. They are attributed to a number of reasons which include nonlinear density dependence due to the finite volume of the molecules, neglected contributions of vibration to the relaxation matrix, and incorrect modeling of interbranch mixing. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469042
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  • 9
    Electronic Resource
    Electronic Resource
    The nature of the absorption bandshape density evolution for the first overtone of CO compressed by N"2
    Amsterdam : Elsevier
    Infrared Physics 34 (1993), S. 289-298 
    Details
    ISSN: 0020-0891
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0020-0891(93)90016-Z
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  • 10
    Electronic Resource
    Electronic Resource
    Infrared spectral absorption intensities in the ν"3 and ν"4 regions of SF"6
    Amsterdam : Elsevier
    Chemical Physics 54 (1980), S. 1-7 
    Details
    ISSN: 0301-0104
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-0104(80)80029-2
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