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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

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

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