Loading...
Derniers dépôts, tout type de 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.
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.
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.
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.
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.
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