Search results for "Quantum"
showing 10 items of 9714 documents
Accurate molecular geometries of the protonated water dimer
2000
The equilibrium geometry of the protonated water dimer, H5O2+, was studied using Moller–Plesset perturbation theory and coupled-cluster theory. Constrained geometry optimizations were carried out for the C2 and Cs symmetric structures within the counterpoise framework and near the limit of a complete basis set. In the constrained optimization, the degrees of freedom of the complex are reduced to an intrafragmental distortion and an interfragmental coordinate, making the procedure tractable for large basis sets and explicitly correlated linear r12 methods. The energy of the stationary point of C2 symmetry was found to be 1.2 kJ mol−1 below the energy of the Cs structure.
Correction: “On-the-fly” coupled cluster path-integral molecular dynamics: impact of nuclear quantum effects on the protonated water dimer
2015
We present an accelerated ab initio path-integral molecular dynamics technique, where the interatomic forces are calculated “on-the-fly” by accurate coupled cluster electronic structure calculations. In this way not only dynamic electron correlation, but also the harmonic and anharmonic zero-point energy, as well as tunneling effects are explicitly taken into account. This method thus allows for very precise finite temperature quantum molecular dynamics simulations. The predictive power of this novel approach is illustrated on the example of the protonated water dimer, where the impact of nuclear quantum effects on its structure and the 1H magnetic shielding tensor are discussed in detail.
New insights in chemical reactivity from quantum chemical topology.
2021
International audience; Based on the quantum chemical topology of the modified electron localization function ELFx, an efficient and robust mechanistic methodology designed to identify the favorable reaction pathway between two reactants is proposed. We first recall and reshape how the supermolecular interaction energy can be evaluated from only three distinct terms, namely the intermolecular coulomb energy, the intermolecular exchange‐correlation energy and the intramolecular energies of reactants. Thereafter, we show that the reactivity between the reactants is driven by the first‐order variation in the coulomb intermolecular energy defined in terms of the response to changes in the numbe…
Temporal incoherent solitons supported by a defocusing nonlinearity with anomalous dispersion
2012
http://pra.aps.org/; International audience; We study temporal incoherent solitons in noninstantaneous response nonlinear media. Contrarily to the usual temporal soliton, which is known to require a focusing nonlinearity with anomalous dispersion, we show that a highly noninstantaneous nonlinear response leads to incoherent soliton structures which require the inverted situation: In the focusing regime (and anomalous dispersion) the incoherent wave packet experiences an unlimited spreading, whereas in the defocusing regime (still with anomalous dispersion) the incoherent wave packet exhibits a self-trapping. These counterintuitive results are explained in detail by a long-range Vlasov formu…
Controlling ground-state rotational dynamics of molecules by shaped femtosecond laser pulses
2004
We report controlled excitation of ground-state rotational wave packet by pulse-shaping technique. The experiment is conducted in nitrogen $({\mathrm{N}}_{2})$ at room temperature and atmospheric pressure. A femtosecond laser pulse produces rotational coherences in the vibronic ground state of ${\mathrm{N}}_{2}$ through an impulsive Raman process. The laser pulse is tailored using a spatial light modulator producing spectral phase modulation. Periodic phase steps are applied in order to control the excitation of specific rotational Raman transitions. The outcome is the modification of the relative excitation between odd and even rotational states which allows the control of the symmetry and…
Integrated plasmonic waveguides: A mode solver based on density of states formulation
2009
International audience; We express the density of states (DOS) near guided resonances of plasmonic waveguides by using multiple-scattering theory. In direct analogy with the case of localized electronic defect states in condensed matter, we demonstrate that optical DOS variations follow a lorentzian profile near guided modes resonances. The lorentzian shape gives quantitative information on the guided modes (effective index, propagation length, and polarization state). We numerically investigate both leaky and bound (lossy) modes supported by dielectric-loaded surface-plasmon-polariton waveguides.
Quantum wire with periodic serial structure
1991
Electron wave motion in a quantum wire with periodic structure is treated by direct solution of the Schr\"odinger equation as a mode-matching problem. Our method is particularly useful for a wire consisting of several distinct units, where the total transfer matrix for wave propagation is just the product of those for its basic units. It is generally applicable to any linearly connected serial device, and it can be implemented on a small computer. The one-dimensional mesoscopic crystal recently considered by Ulloa, Casta\~no, and Kirczenow [Phys. Rev. B 41, 12 350 (1990)] is discussed with our method, and is shown to be a strictly one-dimensional problem. Electron motion in the multiple-stu…
Vacuum Rabi Splitting and Strong-Coupling Dynamics for Surface-Plasmon Polaritons and Rhodamine 6G Molecules
2009
We report on strong coupling between surface plasmon polaritons (SPP) and Rhodamine 6G (R6G) molecules, with double vacuum Rabi splitting energies up to 230 and 110 meV. In addition, we demonstrate the emission of all three energy branches of the strongly coupled SPP-exciton hybrid system, revealing features of system dynamics that are not visible in conventional reflectometry. Finally, in analogy to tunable-Q microcavities, we show that the Rabi splitting can be controlled by adjusting the interaction time between waveguided SPPs and R6G deposited on top of the waveguide. The interaction time can be controlled with sub-fs precision by adjusting the length of the R6G area with standard lith…
Structure of longitudinal chromomagnetic fields in high energy collisions
2014
We compute expectation values of spatial Wilson loops in the forward light cone of high-energy collisions. We consider ensembles of gauge field configurations generated from a classical Gaussian effective action as well as solutions of high-energy renormalization group evolution with fixed and running coupling. The initial fields correspond to a color field condensate exhibiting domain-like structure over distance scales of order the saturation scale. At later times universal scaling emerges at large distances for all ensembles, with a nontrivial critical exponent. Finally, we compare the results for the Wilson loop to the two-point correlator of magnetic fields.
Short range correlations in the weak decay of Lambda hypernuclei.
1995
The differences found in the relativistic and nonrelativistic methods used in the literature to account for short range nuclear correlations in the decay of \ensuremath{\Lambda} hypernuclei are analyzed. By means of a schematic microscopic model for the origin of correlations, the appropriate method to include them in nuclear processes is derived and is found to be the same one used in the nonrelativistic approach. The differences do not stem from relativistic effects but from the improper implementation of the correlations in the relativistic approach, which leads to several pathologies as shown in the paper. General formulas are given to evaluate the nonmesonic decay width of finite hyper…