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Christian Naulin - One of the best experts on this subject based on the ideXlab platform.

  • low energy water hydrogen Inelastic Collisions
    Journal of Physical Chemistry A, 2020
    Co-Authors: Astrid Bergeat, Alexandre Faure, Sebastien B Morales, Audrey Moudens, Christian Naulin
    Abstract:

    New molecular beam scattering experiments are reported for the water–hydrogen system. Integral cross sections of the first rotational excitations of para- and ortho-H2O by Inelastic Collisions with...

  • understanding the quantum nature of low energy c 3 p j he Inelastic Collisions
    Nature Chemistry, 2018
    Co-Authors: Astrid Bergeat, Sebastien B Morales, Christian Naulin, Michel Costes, Simon Chefdeville, Uzi Even, Jacek Klos, Francois Lique
    Abstract:

    Inelastic Collisions that occur between open-shell atoms and other atoms or molecules, and that promote a spin–orbit transition, involve multiple interaction potentials. They are non-adiabatic by nature and cannot be described within the Born–Oppenheimer approximation; in particular, their theoretical modelling becomes very challenging when the collision energies have values comparable to the spin–orbit splitting. Here we study Inelastic Collisions between carbon in its ground state C(3Pj=0) and helium atoms—at collision energies in the vicinity of spin–orbit excitation thresholds (~0.2 and 0.5 kJ mol−1)—that result in spin–orbit excitation to C(3Pj=1) and C(3Pj=2). State-to-state integral cross-sections are obtained from crossed-beam experiments with a beam source that provides an almost pure beam of C(3Pj=0) . We observe very good agreement between experimental and theoretical results (acquired using newly calculated potential energy curves), which validates our characterization of the quantum dynamical resonances that are observed. Rate coefficients at very low temperatures suitable for chemical modelling of the interstellar medium are also calculated. Collision-induced spin–orbit transitions involve multiple interaction potentials and are by nature non-adiabatic, complicating both their experimental and theoretical study. Crossed-beam experiments and non-Born–Oppenheimer quantum calculations for Inelastic Collisions of carbon atoms with helium atoms, down to energies corresponding to temperatures below 10 K, have now been performed. Quantum-dynamical resonances predicted by theory were experimentally detected.

  • observation of quantum dynamical resonances in near cold Inelastic Collisions of astrophysical molecules
    Chemical Science, 2016
    Co-Authors: Christian Naulin, Michel Costes
    Abstract:

    This mini review summarizes experimental findings of quantum dynamical resonances in Inelastic Collisions at energies equivalent to temperatures of a few to a few tens of Kelvin, corresponding to physical conditions prevailing in dense molecular clouds of the interstellar medium. Information obtained is thus relevant to collision energy transfer modelling in such media. Crossed-beam scattering experiments performed at Bordeaux university for Inelastic Collisions of important astrophysical molecules such as CO with H2 or He and O2 with H2 are described. The peaks that show up in the collision energy dependence of the state-to-state integral cross sections for the lowest rotational excitation transitions reveal the quantum nature of such processes. They are ascribed as shape and Feshbach resonances by comparison with the results of close coupling quantum mechanical calculations performed concomitantly on accurate potential energy surfaces.

  • observation of partial wave resonances in low energy o2 h2 Inelastic Collisions
    Science, 2013
    Co-Authors: Christian Naulin, Michel Costes, Simon Chefdeville, Francois Lique, Yulia N Kalugina, Sebastiaan Y T Van De Meerakker
    Abstract:

    Partial wave resonances predicted to occur in bimolecular collision processes have proven challenging to observe experimentally. Here, we report crossed-beam experiments and quantum-scattering calculations on Inelastic Collisions between ground-state O2 and H2 molecules that provide state-to-state cross sections for rotational excitation of O2 (rotational state N = 1, j = 0) to O2 (N = 1, j = 1) in the vicinity of the thermodynamic threshold at 3.96 centimeter(-1). The close agreement between experimental and theoretical results confirms the classically forbidden character of this collision-induced transition, which occurs exclusively in a purely quantum mechanical regime via shape and Feshbach resonances arising from partial waves with total angular momentum (J) = 2 to 4.

  • appearance of low energy resonances in co para h2 Inelastic Collisions
    Physical Review Letters, 2012
    Co-Authors: Simon Chefdeville, Astrid Bergeat, Christian Naulin, Thierry Stoecklin, Kevin M Hickson, Michel Costes
    Abstract:

    We report on crossed-beam experiments and quantum-mechanical calculations performed on the $\mathrm{CO}(j=0)+{\mathrm{H}}_{2}(j=0)\ensuremath{\rightarrow}\mathrm{CO}(j=1)+{\mathrm{H}}_{2}(j=0)$ system. The experimental cross sections determined in the threshold region of the $\mathrm{CO}(j=0\ensuremath{\rightarrow}j=1)$ transition at $3.85\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ show resonance structures in good qualitative agreement with the theoretical ones. These results suggest that the potential energy surface which describes the $\mathrm{CO}\mathrm{\text{\ensuremath{-}}}{\mathrm{H}}_{2}$ van der Waals interaction should be reinvestigated for good quantitative agreement.

Jean-luc Cambier - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of Inelastic Collisions in a multifluid plasma: Ionization and recombination
    Physics of Plasmas, 2016
    Co-Authors: Hai P. Le, Jean-luc Cambier
    Abstract:

    A model for ionization and recombination Collisions in a multifluid plasma is formulated using the framework introduced in previous work [H. P. Le and J.-L. Cambier, Phys. Plasmas 22, 093512 (2015)]. The exchange source terms for density, momentum, and energy are detailed for the case of electron induced ionization and three body recombination Collisions with isotropic scattering. The principle of detailed balance is enforced at the microscopic level. We describe how to incorporate the standard collisional-radiative model into the multifluid equations using the current formulation. Numerical solutions of the collisional-radiative rate equations for atomic hydrogen are presented to highlight the impact of the multifluid effect on the kinetics.

  • modeling of Inelastic Collisions in a multifluid plasma ionization and recombination
    arXiv: Plasma Physics, 2016
    Co-Authors: Jean-luc Cambier
    Abstract:

    A model for ionization and recombination Collisions in a multifluid plasma is formulated using the framework introduced in previous work [{Phys. Plasmas} \textbf{22}, 093512 (2015)]. The exchange source terms for density, momentum and energy are detailed for the case of electron induced ionization and three body recombination Collisions with isotropic scattering. The principle of detailed balance is enforced at the microscopic level. We describe how to incorporate the standard collisional-radiative model into the multifluid equations using the current formulation. Numerical solutions of the collisional-radiative rate equations for atomic hydrogen are presented to highlight the impact of the multifluid effect on the kinetics.

  • Modeling of Inelastic Collisions in a multifluid plasma: Excitation and deexcitation
    Physics of Plasmas, 2015
    Co-Authors: Jean-luc Cambier
    Abstract:

    We describe here a model for Inelastic Collisions for electronic excitation and deexcitation processes in a general, multifluid plasma. The model is derived from kinetic theory, and applicable to any mixture and mass ratio. The principle of detailed balance is strictly enforced, and the model is consistent with all asymptotic limits. The results are verified with direct Monte Carlo calculations, and various numerical tests are conducted for the case of an electron-hydrogen two-fluid system, using a generic, semi-classical model of collision cross sections. We find that in some cases, the contribution of Inelastic Collisions to the momentum and thermal resistance coefficients is not negligible, in contrast to the assumptions of current multifluid models. This fundamental model is also applied to ionization and recombination processes, the studies on which are currently underway.

Yoshiro Takahashi - One of the best experts on this subject based on the ideXlab platform.

  • spin dependent Inelastic Collisions between metastable state two electron atoms and ground state alkali atoms
    New Journal of Physics, 2017
    Co-Authors: Florian Schafer, Hideki Konishi, Adrien Bouscal, Tomoya Yagami, Yoshiro Takahashi
    Abstract:

    Experimentally the spin dependence of Inelastic Collisions between ytterbium (Yb) in the metastable state and lithium (Li) in the ground state manifold is investigated at low magnetic fields. Using selective excitation all magnetic sublevels m J of Yb() are accessed and four of the six lowest lying magnetic sublevels of are prepared by optical pumping. On the one hand, m J -independence of Collisions involving Li() atoms is found. A systematic m J -dependence in Collisions with Li() atoms, in particular suppressed losses for stretched collisional states, is observed on the other hand. Further, m J -changing processes are found to be of minor relevance. The span of observed Inelastic collision rates is between and , and a possible origin of the observed behavior is discussed.

  • Inelastic Collisions in optically trapped ultracold metastable ytterbium
    Physical Review Letters, 2008
    Co-Authors: A Yamaguchi, John M Doyle, Satoshi Uetake, D Hashimoto, Yoshiro Takahashi
    Abstract:

    We report measurement of Inelastic loss in dense and cold metastable ytterbium (Yb[3P2]). Use of an optical far-off-resonance trap enables us to trap atoms in all magnetic sublevels, removing m-changing collisional trap loss from the system. Trapped samples of Yb[3P2] are produced at a density of 2 x 10(13) cm(-3) and temperature of 2 microK. We observe rapid two-body trap loss of Yb[3P2] and measure the Inelastic collision rate constant 1.0(3) x 10(-11) cm3 s(-1). The existence of the fine-structure changing Collisions between atoms in the 3P2 state is strongly suggested.

Bretislav Friedrich - One of the best experts on this subject based on the ideXlab platform.

  • communications when diffraction rules the stereodynamics of rotationally Inelastic Collisions
    Journal of Chemical Physics, 2010
    Co-Authors: Mikhail Lemeshko, Pablo G. Jambrina, Marcelo P. De Miranda, Bretislav Friedrich
    Abstract:

    Following upon our recent work on vector correlations in the Ar–NO Collisions [Lemeshko and Friedrich, Phys. Chem. Chem. Phys. 12, 1038 (2010)], we compare model results with close-coupling calculations for a range of channels and collision energies for the He–NO system. The striking agreement between the model and exact polarization moments indicates that the stereodynamics of rotationally Inelastic atom-molecule Collisions at thermal energies is governed by diffraction of matter waves from a two-dimensional repulsive core of the atom-molecule potential. Furthermore, the model polarization moments characterizing the He–NO, He–O2, He–OH, and He–CaH stereodynamics are found to coalesce into a single, distinctive pattern, which can serve as a “fingerprint” to identify diffraction-driven stereodynamics in future work.

  • an analytic model of rotationally Inelastic Collisions of polar molecules in electric fields
    Journal of Chemical Physics, 2008
    Co-Authors: Mikhail Lemeshko, Bretislav Friedrich
    Abstract:

    We present an analytic model of thermal state-to-state rotationally Inelastic Collisions of polar molecules in electric fields. The model is based on the Fraunhofer scattering of matter waves and requires Legendre moments characterizing the “shape” of the target in the body-fixed frame as its input. The electric field orients the target in the space-fixed frame and thereby effects a striking alteration of the dynamical observables: both the phase and amplitude of the oscillations in the partial differential cross sections undergo characteristic field-dependent changes that transgress into the partial integral cross sections. As the cross sections can be evaluated for a field applied parallel or perpendicular to the relative velocity, the model also offers predictions about steric asymmetry. We exemplify the field-dependent quantum collision dynamics with the behavior of the Ne–OCS(Σ1) and Ar–NO(Π2) systems. A comparison with the close-coupling calculations available for the latter system [Chem. Phys. Lett...

  • an analytic model of rotationally Inelastic Collisions of polar molecules in electric fields
    arXiv: Chemical Physics, 2008
    Co-Authors: Mikhail Lemeshko, Bretislav Friedrich
    Abstract:

    We present an analytic model of thermal state-to-state rotationally Inelastic Collisions of polar molecules in electric fields. The model is based on the Fraunhofer scattering of matter waves and requires Legendre moments characterizing the "shape" of the target in the body-fixed frame as its input. The electric field orients the target in the space-fixed frame and thereby effects a striking alteration of the dynamical observables: both the phase and amplitude of the oscillations in the partial differential cross sections undergo characteristic field-dependent changes that transgress into the partial integral cross sections. As the cross sections can be evaluated for a field applied parallel or perpendicular to the relative velocity, the model also offers predictions about steric asymmetry. We exemplify the field-dependent quantum collision dynamics with the behavior of the Ne-OCS($^{1}\Sigma$) and Ar-NO($^2\Pi$) systems. A comparison with the close-coupling calculations available for the latter system [Chem. Phys. Lett. \textbf{313}, 491 (1999)] demonstrates the model's ability to qualitatively explain the field dependence of all the scattering features observed.

Jinfeng Liao - One of the best experts on this subject based on the ideXlab platform.

  • the subtle interplay of elastic and Inelastic Collisions in the thermalization of the quark gluon plasma
    Nuclear Physics, 2016
    Co-Authors: Jeanpaul Blaizot, Jinfeng Liao, Yacine Mehtartani
    Abstract:

    Abstract Using kinetic theory, we analyze the interplay of elastic and Inelastic Collisions in the thermalization of the quark-gluon plasma. The main focus is the dynamics and equilibration of long wavelength modes.

  • glasma evolution and bose einstein condensation with elastic and Inelastic Collisions
    Physical Review D, 2015
    Co-Authors: Jinfeng Liao, Xuguang Huang
    Abstract:

    In this paper we investigate the role of Inelastic Collisions in the kinetic evolution of a highly overpopulated gluon system starting from a glasma-type initial condition. Using the Gunion-Bertsch formula we derive the Inelastic collision kernel under the collinear and small-angle approximations. With both numerics and analytic analysis, we show that the Inelastic process has two effects: globally changing (mostly reducing) the total particle number, while locally in the small-momentum regime always filling up the infrared modes extremely quickly. This latter effect is found to significantly speed up the emergence of a local thermal distribution in the infrared regime with vanishing local ``chemical potential'' and thus catalyze the onset of dynamical Bose-Einstein condensation to occur faster (as compared with the purely elastic case) in the overpopulated glasma.