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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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The accurate description of an atom or molecule colliding with a metal surface remains challenging. Several strategies have been performed over the past decades to include in a Langevin dynamics the energy transfer related to electron-hole pair excitations in a phenomenological way through a friction contribution. We report the adaptation of two schemes previously developed in the litterature to couple the electronic friction dynamics with the Density-Functional based Tight-Binding (DFTB) approach. The first scheme relies on an electronic isotropic friction coefficient determined from the local electronic density (Local Density Friction Approximation or LDFA). In the second one, a tensorial friction is generated from the non-adiabatic couplings of the ground electronic state with the single electron-hole excitations (Electron Tensor Friction Approximation or ETFA). New DFTB parameterization provides potential energy curves in good agreement with first-principle Density-Functional Theory (DFT) energy calculations for selected pathways of hydrogen atom adsorbing onto the (100) silver surface or penetrating subsurface. Preliminary DFTB/Langevin dynamics simulations are presented for hydrogen atom scattering from the (100) silver surface and energy loss timescales are characterized.

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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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Sujets

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

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168