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  • American Institute of Physics (AIP)  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Reactive collision with excited states in a crossed beam experiment: O(1D)+H2(v)→OH(A 2Σ+)+H (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 7340-7348 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: At least for its most probable mechanisms, the reaction O(1D)+H2(X 1∑+g) →OH(A 2∑+)+H(1 2S) entirely takes place, from reagents to products, on electronically excited-state channels. Due to its endoergicity and to probable energy barriers (E*≈2.8 eV) encountered on these channels, the reaction can be produced in a crossed beam experiment only if the hydrogen molecule is excited on high vibrational levels (v≥5 or v≥7, according to the presence or the absence of energy barriers). This is obtained here by low-energy electron bombardment of the H2 molecular beam. The reaction is observed through the spontaneous fluorescence of the product OH. The measured spectrum corresponding to the 0–0 band of the A 2∑+→X 2Π transition is compared to simulated spectra, as obtained with a simple statistical model and with fitted rotational distribution for OH(A 2∑+,v=0): a broad rotational distribution and a strongly nonstatistical effect on the spin doublet populations are observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458219
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative analysis of third harmonic generation of XUV radiation in a cell and a cw free jet of carbon monoxide (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 5246-5256 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the theory, the two-photon resonant third-order nonlinear susceptibility of a molecular gas is calculated. The variations of this susceptibility, with the rotational quantum numbers of the resonant states, are given in the case of two singlet states of different symmetries, Σ and Π. In the experiment, third harmonic generation of XUV light (94.5–97.5 nm) is obtained with and without two-photon resonance. The gaseous nonlinear medium is formed by CO as used either in a cell, or in a continuous supersonic free jet zone of silence. The intensity of the third harmonic wave generated is well related to the laser power, phase-matching conditions, two-photon resonances, and rotational temperature, through the nonlinear susceptibility, as described theoretically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452548
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  • 3
    Electronic Resource
    Electronic Resource
    Simple model for the electronic relaxation during the expansion of a plasma generated in an Ar–O2 mixture (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 4750-4758 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The local properties of a plasma free jet are calculated with a collisional-radiative model where electron density and temperature are included as parameters. The kinetic equations are written for all the electronic states of the atomic species Ar and O. In the first step, only excitation and de-excitation by electron collisions are taken into account, together with spontaneous radiative decay. This allows the problem to be treated as a linear system of equations represented by a matrix. In the second step, collisional processes with atoms and residual molecules are included. The number of adjustable parameters is limited to the normalization factor of the reaction rate constants for excitation by electrons, the degree of dissociation of oxygen at the nozzle exit, and to the relative number of singly charged ions for oxygen and argon along the axis. Electron temperature and density are measured experimentally, or obtained separately from another calculation. Then, the population density of any level can be obtained in any point of the free jet. The results are compared, on the axis, with those of three different experiments, and the agreement is quite satisfactory in any case. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873762
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  • 4
    Electronic Resource
    Electronic Resource
    Properties of an argon plasma free jet generated from a continuous optical discharge (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2502-2510 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The expansion of a supersonic free jet generated from a laser-sustained argon plasma is studied experimentally by using two techniques: (i) the time-of-flight analysis of velocity distributions of the atom beam skimmed from the free jet, leading to the conclusion that the translational relaxation of the heavy particles (neutral atoms and ions) follows very accurately the classical isentropic laws; (ii) the fluorescence technique for studying the internal state relaxation process by local analysis of the radiation emitted spontaneously from the plasma free jet. Only the electronic states excited above 14.5 eV are found to be in a Boltzmann equilibrium, defining a local temperature Texcit in the structure of the free jet. The axial electronic temperature, calculated using a simple one-dimension thermodynamic model, follows fairly well the experimental values of Texcit, while the translational temperature of the heavy particles decreases much lower, in agreement with the asymptotic value deduced from the velocity distributions of the atom beam. Thus appears the uncoupling between the electronic excitation process, governed by the electronic collisions, and the translational cooling of the heavy particles, governed by the collisions between the heavy particles. A more detailed analysis of the excitation process is obtained through the calculation of the state population densities with a collisional-radiative model. The agreement with the experimental measurements is rather good for most of the states investigated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871968
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