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In this article, we investigate the optical response of a duplicated two-level atomic medium submitted to a strong stationnary control field and a weak co-propagating probe field, orthogonally polarized to each other. We show that both reflected and transmitted components of the probe may be absorbed and amplified. Moreover, for low optical depths, reflection and transmission factors are controlled by the relative phase between control and probe fields, which makes the configuration we present here promising for the development of optical devices, such as phase-controlled switches.

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The sinking of alkali cations in superfluid 4He nanodroplets is investigated theoretically using liquid 4He time-dependent density functional theory at zero temperature. The simulations illustrate the dynamics of the buildup of the first solvation shell around the ions. The number of helium atoms in this shell is found to linearly increase with time during the first stages of the dynamics. This points to a Poissonian capture process, as concluded in the work of Albrechtsen et al. on the primary steps of Na+ solvation in helium droplets [Albrechtsen et al., Nature 623, 319 (2023)]. The energy dissipation rate by helium atom ejection is found to be quite similar between all alkalis, the main difference being a larger energy dissipated per atom for the lighter alkalis at the beginning of the dynamics. In addition, the number of helium atoms in the first solvation shell is found to be lower at the end of the dynamics than at equilibrium for both Li+ and Na+, pointing to a kinetic rather than thermodynamical control of the snowball size for small and strongly attractive ions.

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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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Sujets

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

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168