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  • 1
    Electronic Resource
    Electronic Resource
    Diode laser probing of vibrational, rotational, and translational excitation of CO2 following collisions with O(1D). I. Inelastic scattering (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3277-3288 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time domain diode laser absorption spectroscopy has been used to measure state-specific energy deposition in the vibrational, rotational, and translational degrees of freedom of CO2 following the 248 nm photolysis of ozone in a low pressure mixture of CO2, O3, and O2. Nascent rotational population distributions have been measured in a number of low-lying CO2 vibrational levels, including 0000, 0110, 0220, 0200, 0330, 1000, and 0001. In addition, measurements of CO2 translational excitation have been obtained for the majority of the rovibrational states which were probed. The results suggest that the prompt absorption signals observed so far arise from inelastic scattering between CO2 and the translationally hot O(1D) and O2(1Δ) photofragments rather than electronic quenching of O(1D) to O(3P) by collisions with CO2. Simple calculations indicate that the latter process should provide substantially more CO2 rotational and translational excitation than is observed here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458861
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of translational, rotational, and vibrational energy transfer in collisions between CO2 and hot hydrogen atoms: The three-dimensional "breathing'' ellipsoid model (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 452-465 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Classical scattering of a particle from a three-dimensional "breathing'' ellipsoid is used to model translational, rotational, and vibrational energy transfer in collisions between hot hydrogen atoms and CO2. The model combines the theoretical formalism which describes rotational scattering between a particle and a three-dimensional rigid ellipsoid with a simple scheme to account for the effects of CO2 vibrational excitation. The calculations are used to analyze experimental data (measured using time-domain diode laser absorption spectroscopy) concerning the state-specific deposition of energy among the translational, rotational, and vibrational degrees of freedom of CO2 following collisions with translationally hot H atoms. The model provides substantial insight into the features of the final-state-resolved experimental data, indicating which "types'' of trajectories, e.g., "end-on'' vs "broadside'' collisions, are responsible for scattering into particular final states. Despite its simplicity, the model is shown to predict virtually all of the major features of the experimental data with remarkable accuracy. In addition, it reproduces highly complex behavior seen in the state–to–state collision cross sections which had been previously obtained using a data-inversion procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459544
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Sensitivity analysis of mass effects in rotational energy transfer (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6322-6334 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper examines the sensitivity of rotationally inelastic integral state-to-state cross sections to variations in the masses of the collision partners. We investigate the helium-hydrogenic scattering system with its many physical isotopes and excellent ab initio potential. The collision dynamics are approximated by coupled states-exponential distorted wave (CS-EDW) theory and both cross sections and elementary sensitivity coefficients (partial derivatives of the cross sections with respect to the mass parameters) are calculated. In order to be able to properly interpret these results, we first generate conceptually and computationally simpler distorted wave (CS-DW) cross sections and elementary sensitivities. These perturbative results are analyzed using simple collisional concepts and models. In addition, we present functional forms which predict (or scale) the global behavior of DW cross sections through the mass parameter space. As a quantitative aid in linking EDW cross sections with the DW results, a new type of sensitivity coefficient is introduced which measures the sensitivity of a given EDW cross section to the variation of a single DW cross section or combination thereof.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454470
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  • 4
    Electronic Resource
    Electronic Resource
    Inversion of experimental data to generate state-to-state cross sections for rovibrationally inelastic scattering of CO2 by hot hydrogen atoms (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 347-357 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: State-to-state integral cross sections for rovibrationally inelastic collisions between CO2 and hot hydrogen atoms are obtained by inversion of rotationally resolved population measurements of CO2 (0001). The inversion/fitting procedure is based upon the infinite order sudden (IOS) scaling law and employs a spline interpolating model to reduce the amount of information to be extracted. The experimental data used in the analysis was obtained using time domain tunable diode laser absorption spectroscopy to measure rotationally resolved excitation in CO2 (0001) following the generation of translationally hot H atoms via H2S photolysis at 193 nm. The analysis utilizes data acquired at two temperatures, 292 and 223 K, in order to acquire additional information about the temperature independent scattering cross sections. Sensitivity analysis is employed to gauge the sensitivity of the extracted cross sections to uncertainties in the experimental data, and also to estimate the effect of additional measurements at different temperatures. The final extracted cross sections exhibit strong rotational inelasticity, with a propensity for scattering from 0000; J' to both 0001; J=J' and 0001; J=||J'±41||. The largest state-to-state collision cross section corresponds to the (0000; J'=0) to (0001; J=41) transition and has a magnitude of (2.0±0.4)×10−3 A(ring)2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458436
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  • 5
    Electronic Resource
    Electronic Resource
    Probing the O(1D)+CO2 reaction with second-derivative modulated diode laser spectroscopy (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7550-7556 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction of electronically excited O(1D) atoms with CO2 to form CO+O2(1Σ+g,1Δg,3Σ−g) has been probed with second-derivative modulated diode laser spectroscopy. The O(1D) atoms were generated by the pulsed 193 nm laser photolysis of N2O, and the reaction was followed by monitoring the formation of CO as a function of the number of laser pulses. These experiments have revealed that the quantum yield for this reaction is (2.1±0.3)×10−3 molecules/photon absorbed. The very low quantum efficiency suggests that a significant potential barrier exists on the reaction coordinate which prevents the vast majority of collisions from fragmenting into products distinguishable from reactants. The rate constant, measured indirectly by comparison with the rate constant for quenching, is found to be (2.4±0.5)×10−13 cm3 molecule−1 s−1 and represents the best estimate currently available in the literature for the reaction rate constant. In experiments involving 16O(1D)+12C18O2, the resulting product, 12C18O, indicates that no isotopic exchange takes place in the reaction. Comparison with deactivation results suggests that the reaction proceeds by a simple, direct oxygen-atom abstraction with a potential barrier, whereas the quenching channel involves a long-lived intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457278
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  • 6
    Electronic Resource
    Electronic Resource
    Hierarchical fitting and scaling models for rotationally inelastic cross sections (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1701-1710 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new method of scaling inelastic cross sections is presented which uses an intermediate-level parametrization of the collision dynamics. By expressing the scattering matrix as exp[−iB] and approximating B with a parametrized functional form, this procedure yields a unitary scaled S matrix and incorporates infinite-order rotational coupling into the scaled results. The inclusion of high order collision dynamics enables the scaled cross sections to exhibit physical behavior which is substantially more realistic and flexible than that allowed by traditional fitting methods. The intermediate level scaling procedure accurately produces complete matrices of rotationally inelastic cross sections for He–HD scattering generated from subsets of input cross sections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456063
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  • 7
    Electronic Resource
    Electronic Resource
    State-resolved vibrational, rotational, and translational energy deposition in CO2(0001) excited by collisions with hot hydrogen atoms (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4876-4886 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-domain tunable diode laser absorption spectroscopy has been used to measure rotationally resolved transient absorption line shapes and nascent rotational populations for CO2 molecules excited into the (0001) vibrational state by collisions with translationally hot hydrogen atoms. High-accuracy measurements were made at both 292 and 223 K, providing information about the initial-state dependence of the collision dynamics and about the (temperature-independent) state–to–state scattering cross sections. The nascent rotational population distribution is found to be nearly independent of temperature, indicating broad rotational inelasticity in the 0000→0001 scattering process. The nascent populations and transient linewidths are interpreted in terms of two separate theoretical models which lend substantial insight into the H–CO2 collision dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457704
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  • 8
    Electronic Resource
    Electronic Resource
    IR diode laser study of vibrational energy distribution in CO2 produced by UV excimer laser photofragmentation of pyruvic acid (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4598-4605 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time domain absorption spectroscopy using a tunable, infrared diode laser has been used to monitor the vibrational excitation of CO2 produced in the 193 nm excimer laser photolysis of gas phase pyruvic acid (CH3COCOOH). Nascent vibrational populations were measured in the following ten vibrational states of CO2: 0000, 0110, 0220, 0330, 0440, 0001, 0002, 0003, 0111, and 0221. Approximately 97% of the CO2 photoproduct is observed to be directly formed in the vibrational ground state. The remaining molecules are formed with a significant degree of vibrational excitation, having mode temperatures T(ν2)=1800±150 K, T(ν3)=3700 ±1000 K, T(ν2+ν3)=2000±400 K. The present experimental data suggest that the 193 nm photolysis may proceed through more than a single dissociation channel and involve a number of different photofragments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453711
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  • 9
    Electronic Resource
    Electronic Resource
    Collisional excitation of CO2(0111) by hot hydrogen atoms: Alternating intensities in state-resolved vibrational, rotational, and translational energy transfer (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 445-451 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time domain tunable diode laser absorption spectroscopy has been used to measure rotationally resolved transient absorption line shapes and nascent rotational populations for CO2 molecules excited into the (0111) vibrational state by collisions with translationally hot hydrogen atoms. The even rotational levels are more heavily populated than the odd levels, in agreement with propensity rules derived earlier by Alexander and Clary. The nascent populations and transient linewidths are interpreted in terms of a theoretical model that lends insight into the H–CO2 collision dynamics. The cross section for exciting (0111) is ∼0.23 times the cross section for exciting (0001), and ∼0.38 times the cross section for exciting (1000).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459718
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  • 10
    Electronic Resource
    Electronic Resource
    Mass effects and channel coupling sensitivity in vibrational energy transfer (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1711-1719 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper examines the mass dependences of vibrationally inelastic integral state-to-state cross sections for the helium-hydrogenic scattering system. The cross sections are calculated within the coupled states-exponential distorted wave (CS-EDW) approximation, and are analyzed along with the conceptually simpler distorted wave (CS-DW) cross sections. Quantitative links between the EDW and DW results are made by means of component (or channel coupling) sensitivity coefficients, which measure the sensitivity of a given EDW cross section to the potential matrix elements coupling any two states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456064
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    Paper (German National Licenses)
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