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  • Elsevier  (35)
  • American Institute of Physics (AIP)  (17)
  • Copernicus  (15)
  • 2010-2014  (36)
  • 2000-2004  (18)
  • 1990-1994  (7)
  • 1985-1989  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Line broadening, line shifting, and line coupling effects on N2–H2O stimulated Raman spectra (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5916-5925 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In order to understand the influence of H2O on the stimulated Raman Q-branch spectra of nitrogen in combusting media, an exhaustive theoretical and experimental study has been carried out. Starting from a semiclassical model, particularly convenient at high temperature, the Q-line broadening and shifting coefficients have been calculated over a wide temperature range and for a large number of lines. Stimulated Raman Spectra (SRS) measurements have allowed us to test these calculated line broadening coefficients and thus establish the high accuracy of semiclassical values. The theoretical broadening coefficients have been inverted to deduce state-to-state rotational relaxation rates by using two types of fitting laws. A partial test of the resulting Q-branch profiles has been realized at moderate pressures leading to a discrimination between these two laws. Furthermore, the effect of rotational energy transfers on collisionally narrowed profiles at higher densities has been simulated and compared with the pure N2 case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457461
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  • 2
    Electronic Resource
    Electronic Resource
    Collision-induced population transfer in infrared absorption spectra. III. Temperature dependence of absorption in the Ar-broadened wing of CO2 ν3 band (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2217-2221 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present experimental and theoretical results on the absorption in the Ar-broadened wing of the infrared CO2 ν3 band. Measurements have been made in the 293–765 K temperature range for total gas pressures up to 60 bar and are in good agreement with previous determinations at room temperature. Calculations have been carried out by using a line by line coupling theory presented and tested previously [J. Chem. Phys. 89, 625 (1988) and 91, 2163 (1989)]. The theoretical approach accounts for both line mixing and the wave-number dependence of the relaxation operator. It enables correct modeling of the temperature dependence of absorption. The strong sublorentzian absorption resulting from competitions between negative and positive individual line contributions is analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459054
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements and calculations of CO2 room-temperature high-pressure spectra in the 4.3 μm region (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2944-2950 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Measurements of the absorption by pure CO2 in the 4.3 μm region are presented. They refer to the temperature of 291 K and densities in the 1–80 amagat range. Calculations based on the addition of Lorentzian contributions strongly overestimate the absorption since they do not account for line overlapping. The energy corrected sudden approximation (ECSA) is used to model line mixing within the impact approximation. The scaling parameters of this model are deduced from line-broadening data. This calculation strongly underestimates the absorption in the spectral region near the edges of the vibrational band, whereas it overestimates the absorption in the far wings of the lines. This is attributed to the impact approximation which does not account for the frequency dependence of the relaxation operator. This dependence is roughly determined from our results; it is in good qualitative agreement with the few corresponding available results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455894
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray standing wave study of MnTe fractional monolayers inserted in CdTe (001) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4889-4897 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The x-ray standing wave method is used in correlation with reflection high-energy electron diffraction and scanning tunneling microscopy to investigate the crystallographic features of MnTe monolayers inserted in CdTe (001). Either conventional molecular beam epitaxy or atomic layer epitaxy were employed for the formation of the CdTe starting surface, the deposition of the MnTe fractional monolayer, and its encapsulation by CdTe. Significant differences concerning the ratio of Mn atoms involved in MnTe clusters to those incorporated as part of a CdMnTe alloy are observed between the samples. Those differences are due to differing CdTe starting surface roughness. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311829
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  • 5
    Electronic Resource
    Electronic Resource
    State-to-state rotational cross sections in vibrational modes. Application to the infrared Q-branch profile for the (11 10)I←(00 00) 12C16O2 bending band (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 3747-3753 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Direct connection between spectroscopic relaxation cross sections and appropriate state-to-state rotational cross sections in vibrational modes enables one to introduce convenient energy corrections to the sudden approximation. Since the angular momentum coupling photon–rotation–vibration is properly taken into account, this approach applies to stretching as well as bending bands. Diode laser experiments have been made for pure 12C16O2 in the infrared Q branch of the (11 10)I←(00 00) band in order to investigate the effect of collisional line mixing on the spectral profile. The energy corrected sudden scaling law is used within the present theoretical approach for both the inversion of j→0 basis cross sections from broadening data and the calculation of line-coupling coefficients. Resulting absorption profiles are in good agreement with measured values without the need for the introduction of any ad hoc decoupling factor for the considered bending band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464053
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  • 6
    Electronic Resource
    Electronic Resource
    A molecular beam/surface spectroscopy apparatus for the study of reactions on complex model catalysts (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 4395-4408 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a newly developed ultrahigh vacuum (UHV) experiment which combines molecular beam techniques and in situ surface spectroscopy. It has been specifically designed to study the reaction kinetics and dynamics on complex model catalysts. The UHV system contains: (a) a preparation compartment providing the experimental techniques which are required to prepare and characterize single-crystal based model catalysts such as ordered oxide surfaces or oxide supported metal particles; and (b) the actual scattering chamber, where up to three molecular beams can be crossed on the sample surface. Two beams are produced by newly developed differentially pumped sources based on multichannel arrays. The latter are capable of providing high intensity and purity beams and can be modulated by means of a vacuum-motor driven and computer-controlled chopper. The third beam is generated in a continuous or pulsed supersonic expansion and is modulated via a variable duty-cycle chopper. Angular and time-resolved measurements of desorbing and scattered molecules are performed with a rotatable doubly differentially pumped quadrupole mass spectrometer with a liquid-nitrogen cooled ionizer housing. Time-resolved but angle-integrated measurements are realized with a second nondifferentially pumped quadrupole mass spectrometer. In situ measurements of adsorbed species under reaction conditions are performed by means of an adapted vacuum Fourier transform infrared spectrometer. The spectrometer provides the possibility of time-resolved measurements and can be synchronized with any of the beam sources. This contribution provides a general overview of the system and a description of all new components and their interplay. We also present test data for all components employing simple adsorption/desorption and reaction systems. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1318919
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  • 7
    Electronic Resource
    Electronic Resource
    Interface dilution and morphology of CdTe/MnTe superlattices studied by small- and large-angle x-ray scattering (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7266-7274 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed small- and large-angle x-ray scattering experiments on CdTe/MnTe superlattices. The Fresnel optical method and the distorted wave Born approximation were used to extract from small-angle measurements out-of-plane and in-plane information about the interfaces. Specular reflectivity shows that the interface roughness is quite high (about 7 Å) for all superlattices. The effective MnTe concentration, directly determined from the refractive index profile, is successfully used to simulate the structured nonspecular scattering, and to determine the lateral correlation length of the interface roughness (about 1500±750 Å). Moreover, it is shown that the layers are almost completely correlated over the sample thickness. The thickness fluctuations along the growth direction are estimated from the analysis of the large-angle (004) reflection, and the effective MnTe profile is also checked by dynamical simulation. It is shown that the small- and large-angle results are in good agreement. The MnTe profile width deduced from x-ray reflectivity is slightly overestimated due to the large integration area of this technique. An estimation of the local MnTe profile is given. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372979
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  • 8
    Electronic Resource
    Electronic Resource
    Experimental and theoretical study of line mixing in methane spectra. IV. Influence of the temperature and of the band (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 5776-5783 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Line-mixing effects are studied in infrared bands of CH4 perturbed by N2 at various pressures. The effects of temperature are investigated in the ν3 region whereas spectral shapes of the ν2, ν4, and ν3 bands are compared at room temperature. The theoretical approach proposed in preceding papers is used in order to model and analyze the influence of collisions on the spectral shape. All model parameters are now fixed to values determined in the previous studies. Comparisons between measurements and spectra computed with and without the inclusion of line mixing are made. They show that our approach satisfactorily accounts for the effects of temperature, pressure, and of rotational quantum numbers on the absorption by the ν3 band. Furthermore, the effects of collisions on spectra in the ν4 region at room temperature are also correctly calculated. On the other hand, the proposed approach fails in modeling the evolution with increasing pressure of absorption in the spectral range containing the ν2 band. This result is attributed to the Coriolis coupling between the ν2 and ν4 vibrational states and to a contribution whose physical origin remains unclear. The latter, which is negligible when CH4–He mixtures are considered, behaves as collision-induced absorption. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289243
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  • 9
    Electronic Resource
    Electronic Resource
    Line shape parameters for HF in a bath of argon as a test of classical path models (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 9000-9010 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The classical path method proposed by Neilsen and Gordon [J. Chem. Phys. 58, 4131 (1973)] is tested by comparison with extensive fully quantal calculations and recent measurements of cross-sections for HF-Ar. Widths and shifts are found to be in satisfactory agreement both with the close-coupling and experimental results. Comparisons are also made with more "downgraded" theoretical approaches based on the peaking approximation and the neglect of the time ordering. Finally, the Neilsen and Gordon approach is used in order to demonstrate that vibration-rotation coupling significantly contributes to the rotational dependence of both widths and shifts cross-sections. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319346
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  • 10
    Electronic Resource
    Electronic Resource
    Collisional broadening of rotation–vibration lines for asymmetric-top molecules. II. H2O diode laser measurements in the 400–900 K range; calculations in the 300–2000 K range (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 144-156 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Numerous comparisons between predictions of the model presented in part I of this paper and experimental H2O infrared linewidths are presented. It is shown that our model, contrary to those used up to now, gives accurate results for H2O room-temperature line broadening by O2 and Ar, and for high rotational quantum-number lines by N2. First accurate experimental widths and intensities of some H2O ν2-band lines in the 400–900 K temperature range are also presented. Detailed analysis of the data demonstrates the great influence of a "resonance overtaking'' mechanism. The latter results from the modifications of both the perturber rovibrational population distribution and kinetic energy with temperature; it strongly enhances the contributions of the collision-induced rotational transitions involving significant energy jumps. This mechanism is well accounted for by our model and quantitatively explains the unusually slow decrease of some linewidths with temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452605
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