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Interactions between molecular hydrogen and ions are of interest in cluster science, astrochemistry and hydrogen storage. In dynamical simulations, H2 molecules are usually modelled as point particles, an approximation that can fail for anisotropic interactions. Here, we apply an adiabatic separation of the H2 rotational motion to build effective pseudoatom-ion potentials and in turn study the properties of (H2)nNa+/Cl− clusters. These interaction potentials are based on high-level ab initio calculations and Improved Lennard-Jones parametrizations, while the subsequent dynamics has been performed by quantum Monte Carlo calculations. By comparisons with simulations explicitly describing the molecular rotations, it is concluded that the present adiabatic model is very adequate. Interestingly, we find differences in the cluster stabilities and coordination shells depending on the spin isomer considered (para- or ortho-H2), especially for the anionic clusters.

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Recent experiments have shown that translational energy loss is mainly mediated by electron–hole pair excitations for hydrogen atoms impinging on clean metallic surfaces. Inspired by these studies, quasi-classical trajectory simulations are here performed to investigate the energy transfer after scattering of hydrogen atoms off clean and hydrogen-covered tungsten (100) surfaces. The present theoretical approach examines the coverage effect of the preadsorbed hydrogen atoms, as was done recently for the (110) crystallographic plane in (J Phys Chem C 125:14075, 2021). As suggested, scattering can be described in terms of three different dynamical mechanisms, the contribution of which changes with coverage, which allow to rationalize the shape of the energy loss spectra.

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We present quasi-classical trajectory calculations of the F + HCl reactive scattering, for total angular momentum equal zero and using a London–Eyring–Polanyi–Sato potential energy surface specifically developed for the title reaction. The reactive dynamics is investigated for a wide range of collision energies, from subthermal velocities up to kinetic energies significantly exceeding the dissociation energy of the reactant molecule. We focus here on the light- and heavy-atom exchange probability and mechanisms at hyperthermal collision velocities, whereas low-energy collisions (which dominate the evaluation of the reaction rate constant) are used for the purpose of validating the current implementation of the quasi-classical trajectory method in a symmetrical hyperspherical configuration space. In spite of the limitations of the potential energy surface, the present methodology yields reaction probabilities in agreement with previous experimental and theoretical results. The computed branching probabilities among the different reaction channels exhibit a mild dependence on the initial vibrational state of the diatomic molecule. Conversely, they show a marked sensitivity to the value of the impact angle, which becomes more pronounced for increasing collision energies.

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The triatomic system NeI2 is studied under the consideration that the diatom is found in an excited electronic state (B). The vibrational levels (v=13, …, 23) are considered within two well-known theoretical procedures: quasi-classical trajectories (QCT), where the classical equations of motion for nuclei are solved on a single potential energy surface (PES), and the trajectory surface hopping (TSH) method, where the same are solved in a bunch of crossed vibrational PES (diabatic representation). The trajectory surface hopping fewest switches (TSHFS) is implemented to minimize the number of hoppings, thus allowing the calculations of hopping probability between the different PES's, and the kinetic mechanism to track the dissociation path. From these calculations, several observables such as, the lifetimes, vibrational and rotational energies (I2), dissociation channels, are obtained. Our results are compared with previous experimental and theoretical work.

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Cold Rydberg atoms are a promising platform for quantum technologies and combining them with optical waveguides has the potential to create robust quantum information devices. Here, we experimentally observe the excitation of cold rubidium atoms to a large range of Rydberg S and D states through interaction with the evanescent field of an optical nanofiber. We develop a theoretical model to account for experimental phenomena present such as the AC Stark shifts and the Casimir-Polder interaction. This work strengthens the knowledge of Rydberg atom interactions with optical nanofibers and is a critical step toward the implementation of all-fiber quantum networks and waveguide QED systems using highly excited atoms.

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Sujets

Collisions des atomes CAVITY DEMO QUANTUM OPTIMAL-CONTROL Muonic hydrogen Bohmian trajectories AR MCTDH Dissipation DRIVEN Dynamique moléculaire quantique Dynamique non-adiabatique ALGORITHM Casimir effect Photophysics COLLISION ENERGY COMPLEX ABSORBING POTENTIALS DISSIPATION 4He-TDDFT simulation Anisotropy DYNAMICS Atomic clusters Théorie de la fonctionnelle de la densité Dynamique quantique Slow light Quantum dynamics Effets de propagation COHERENT CONTROL Ejection Dark energy Cryptochrome Effets inélastiques Cluster Transport électronique DIFFERENTIAL CROSS-SECTIONS Ab-initio STATE Dissipative dynamics Coulomb presssure Coherent control Molecules Density functional theory Composés organiques à valence mixte Electric field Effets transitoires Atom Extra dimension CHEMICAL-REACTIONS Rydberg atoms CLASSICAL TRAJECTORY METHOD Agrégats Wave packet interferences Ab initio calculations Collisions ultra froides Coordonnées hypersphériques elliptiques Electron-surface collision Propagation effects ENTANGLEMENT ELECTRON-NUCLEAR DYNAMICS Clusters DEPENDENT SCHRODINGER-EQUATION Non-equilibrium Green's function Cope rearrangement ELECTRONIC BUBBLE FORMATION Anharmonicity Atomic scattering from surfaces Dynamics Fonction de Green hors-équilibre ELECTRON DYNAMICS Electronic Structure CONICAL INTERSECTION Tetrathiafulvalene Dissipative quantum methods Theory Collision frequency ENERGY DENSITY Deformation Atomic collisions DFTB Superfluid helium nanodroplets Effets isotopiques Electronic transport inelastic effects Alkali-halide WAVE-PACKET DYNAMICS Half revival Electron transfer Cesium Drops ENTROPY Classical trajectory Ultrashort pulses Contrôle cohérent Close-coupling Dynamique mixte classique MODEL Calcium Diels-Alder reaction Transitions non-adiabatiques Cosmological constant

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