index - Théorie Access content directly

Last deposit, any kind of documents

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.

Continuer la lecture Partager

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.

Continuer la lecture Partager

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.

Continuer la lecture Partager

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.

Continuer la lecture Partager

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.

Continuer la lecture Partager


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


Number of files submitted


Number of notices submitted