Long-range interactions in the ozone molecule: spectroscopic and dynamical points of view

Using the multipolar expansion of the electrostatic energy, we have characterized the asymptotic interactions between an oxygen atom O$(^3P)$ and an oxygen molecule O$_2(^3\Sigma_g^-)$, both in their electronic ground state. We have calculated the interaction energy induced by the permanent electric quadrupoles of O and O$_2$ and the van der Waals energy. On one hand we determined the 27 electronic potential energy surfaces including spin-orbit connected to the O$(^3P)$ + O$_2(^3\Sigma_g^-)$ dissociation limit of the O--O$_2$ complex. On the other hand we computed the potential energy curves characterizing the interaction between O$(^3P)$ and a O$_2(^3\Sigma_g^-)$ molecule in its lowest vibrational level and in a low rotational level. Such curves are found adiabatic to a good approximation, namely they are only weakly coupled to each other. These results represent a first step for modeling the spectroscopy of ozone bound levels close to the dissociation limit, as well as the low energy collisions between O and O$_2$ thus complementing the knowledge relevant for the ozone formation mechanism.Comment: Submitted to J. Chem. Phys. after revisio

Structure électronique du système HCO / COH et étude de la réaction entre le carbone et le radical OH dans leur état fondamental

Cette thèse porte sur l étude théorique de la collision réactive entre les radicaux C et OH dans leur état fondamental pour des températures inférieures a 500 K. Tout d abord, l énergie potentielle du système HCO/COH dans son état fondamental a été calculée pour un grand nombre de géométries en utilisant des méthodes ab initio de haut niveau. Ces valeurs ont ensuite été interpolées par la méthode RKHS afin de construire une forme analytique de la surface d énergie potentielle globale du système. Cette surface a été utilisée pour étudier la dynamique de la réaction entre C et OH avec la méthode des trajectoires quasi-classiques. Les résultats obtenus ont mis en évidence le caractère fortement réactif de la collision entre ces deux radicaux, même à basse température. Une étude préliminaire des états électroniques excités du système et de leurs couplages est également présentée et montre que certains d entre eux peuvent avoir une contribution sur la dynamique de la réaction.This thesis concerns the theoretical study of the reactive collision between the radicals C and OH in their ground state for temperatures below 500 K. The potential energy of the HCO/COH system in its ground state was first computed for a large number of geometries using high level ab initio methods. The energies were then fitted using the RKHS method to build an analytic form for the global potential energy surface of the system. The surface was then used to study the reaction dynamics of C and OH by the quasi-classical trajectories method. The results obtained show the strong reactivity of the collision of these radicals even at low temperature. A preliminary study of the excited states and of their couplings is also presented and it shows that some of them may play an important role in the reaction dynamics.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Some results about the C2H2-H2 and C2H2-N2 systems

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Time-dependent wave packet and quasiclassical trajectory study of the C(3P)+OH(X 2)CO(X 1+)+H(2S) reaction at the state-to-state level

9 pages, 9 figures, 1 table.The first calculations of state-to-state reaction probabilities and product state-resolved integral cross sections at selected collision energies (0.05, 0.1, 0.5, and 1.0 eV) for the title reaction on the ab initio potential energy surface of [Zanchet et al. J. Phys. Chem. A 110, 12017 (2006)] with the OH reagent in selected rovibrational states (v=0–2, j=0–5) have been carried out by means of the real wave packet (RWP) and quasiclassical trajectory (QCT) methods. State-selected total reaction probabilities have been calculated for total angular momentum J=0 in a broad range of collision energies. Integral cross sections and state-specific rate coefficients have been obtained from the corresponding J=0 RWP reaction probabilities for initially selected rovibrational states by means of a capture model. The calculated RWP and QCT state-selected rate coefficients are practically temperature independent. Both RWP and QCT reaction probabilities, integral cross sections, and rate coefficients are almost independent of the initial rotational excitation. The RWP results are found to be in an overall good agreement with the corresponding QCT results. The present results have been compared with earlier wave packet calculations carried out on the same potential energy surface.Partial financial support from the Spanish Ministry of Education and Science (Project No. CTQ2008-02578/BQU) is gratefully acknowledged. A.Z., P.H., and B.B.-H. acknowledge support from the Institut du Développement des Ressources en Informatique Scientifique (IDRIS) in Orsay (France), the UTINAM laboratory for its fast cluster, and also the Pôle de Sciences Planétaires of Bourgogne Franche-Comté.Peer reviewe

Study of the C + OH --> CO + H reaction: fully global ab initio potential energy surfaces of the 12A'' and 14A'' excited states and non adiabatic couplings

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Differential cross sections and product energy distributions for the C + OH -> CO + H reaction using a quasi-classical trajectory method

Quasiclassical trajectory calculations have been carried out for the C((3)P)+OH(X (2)Pi)-->CO(X (1)Sigma(+))+H((2)S) reaction using a recent ab initio potential energy surface for the ground electronic state X (2)A(') of COH. Differential cross sections (DCSs), and product vibrational, rotational and translational distributions have been determined for a wide range of collision energies (0.001-1 eV). The role of excitations (rotation or vibration) of the OH reactant on these quantities has been investigated. Product vibrational, rotational, and translational distributions are found to be almost independent on the rovibrational state of OH, whereas DCSs show a weak dependence on the initial rotational state of OH. We also analyze the results using a study based on the lifetime of the intermediate complex and on the kinematic constraint associated with the mass combination

Study of the C + OH --> CO + H reaction: fully global ab initio potential energy surfaces of the 12A'' and 14A'' excited states and non adiabatic couplings

International audienceWe report in this paper ab initio calculations of the potential energy surfaces (PESs) for the four states involved in the C(3P) + OH(X2Π)→ CO(a3Π) + H(2S) reaction as well as numerical values of the rate constants for two states, 12A″ and 14A″ which show no potential barriers during the reaction. In contrast, the other two states, i.e. the 22A′ and 14A′ states, are energetically not favourable to the reaction as the first state has a potential barrier of 0.2 eV in the entrance channel and the former one presents long range potential wells and repulsive wall for carbon approaches near OH. The ab initio calculations of the potential energies have been performed at the multireference internally contracted single and double configuration interaction (MR-SDCI) level corrected for its size-inconsistency by the Davidson method (+Q), and using Dunning aug-cc-pVQZ atomic basis sets. Global PESs have then been generated for the two A″ states from an analytical fit obtained with the reproducing kernel Hilbert space method on a large number of ab initio points located on a regular grid in Jacobi coordinates. The title reaction is much less exoergic (−0.41 eV) than the one on the ground state and each state presents many extrema (four for the 12A″ and eight for the 14A″). From the configuration and energy of these extrema, different reaction mechanisms are suggested depending on the collision energy. Quasi-classical trajectory calculations on these global PESs have been used to estimate reactive cross-sections as functions of the collision energy and thermal rate constant as a function of the temperature. The weighted rate constant for each state, i.e. including the spin–orbit population factor, increases with the temperature contrary to the ground state one. Nevertheless, a decreasing behaviour with the temperature remains between 10 and 500 K if we consider the total rate constant of C(3P) + OH(X2Π), sum of the three reactive states rate constants

Nonadiabatic quantum dynamics of C(1D)+H2 --> CH+H : Coupled-channel calculations including Renner-Teller and Coriolis terms

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Differential cross sections and product energy distributions for the C + OH -> CO + H reaction using a quasi-classical trajectory method

Quasiclassical trajectory calculations have been carried out for the C((3)P)+OH(X (2)Pi)-->CO(X (1)Sigma(+))+H((2)S) reaction using a recent ab initio potential energy surface for the ground electronic state X (2)A(') of COH. Differential cross sections (DCSs), and product vibrational, rotational and translational distributions have been determined for a wide range of collision energies (0.001-1 eV). The role of excitations (rotation or vibration) of the OH reactant on these quantities has been investigated. Product vibrational, rotational, and translational distributions are found to be almost independent on the rovibrational state of OH, whereas DCSs show a weak dependence on the initial rotational state of OH. We also analyze the results using a study based on the lifetime of the intermediate complex and on the kinematic constraint associated with the mass combination

Photoassociation of cold calcium atoms through the A^{1}Σ_{u}^{+}(1^{1}D+1^{1}S),c^{3}Π_{u}(1^{3}P+1^{1}S), and a^{3}Σ_{u}^{+}(1^{3}P+1^{1}S) states: An ab initio nonadiabatic treatment

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