Search results for "Linear"
showing 10 items of 7165 documents
Using molecular alignment to track ultrafast collisional relaxation
2014
Field-free molecular alignment has been used in order to track the collisional relaxation occurring in a molecular gas. CO${}_{2}$ molecules were initially irradiated by a short linearly polarized laser pulse resulting in the increase of their rotational energy. The evolution of the subsequent ultrafast relaxation process was optically probed after irradiating the sample with a second, weaker, short pulse leading to the alignment of the preheated molecules. Using classical molecular dynamic simulations, we were able to quantitatively reproduce the experimental shapes and amplitudes of the recorded revival transients for a time interval extending from 25 to 500 ps until thermalization of the…
RPA in wavefunction representation
1992
The RPA is formulated in subspaces of coordinate-like and momentum-like I ph operators. This allows to embed a large class of approximative schemes into a generalized RPA treatment. We give a detailed formulation in terms of wavefunctions in coordinate space which is ideally suited to practical programming. In particular, we work out the reduction to spherical tensors in the case of spherical symmetry which is most often the starting point in finite Fermion systems.
Relativistic Effects and Two-Body Currents inH2(e→,e′p)nUsing Out-of-Plane Detection
2001
Measurements of the (2)H((-->)e,e(')p)n reaction were performed with the out-of-plane magnetic spectrometers (OOPS) at the MIT-Bates Linear Accelerator. The longitudinal-transverse, f(LT) and f(')(LT), and the transverse-transverse, f(TT), interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q2 = 0.15 (GeV/c)(2). In comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions and the importance of two-body meson-exchange currents and isobar configurations. We demonstrate that such effects can be disentangled by extracting these responses using the novel out-of…
Monte Carlo Simulation of Harmonic Generation in GaAs structures operating under large-signal Conditions
2007
By using a multiparticles Monte Carlo technique, with a self-consistently coupled one-dimensional Poisson solver, we investigate the dependence of the nonlinear carrier dynamics in GaAs n+nn+ micro e submicro-structures operating under very intense sub-terahertz signals by: (i) the frequency and the intensity of the excitation signal and (ii) the length of the n region.
Multimode emission in inhomogeneously broadened ring lasers
2001
The threshold for multilongitudinal-mode emission in inhomogeneously broadened ring lasers is analytically investigated. In the homogeneous limit the multimode instability corresponds to the classical Risken–Nummedal–Graham–Haken instability. It is found that by increasing the inhomogeneous linewidth, the instability threshold is decreased and the growth of high-frequency side modes is favored. In the limit where the population-inversion decay rate γ‖ is much smaller than the polarization decay rate γ⊥ (class B lasers), analytical expressions for the instability threshold are found, which are then generalized to three-level lasers for a comparison with experimental results obtained with erb…
Stabilization of 1D solitons by fractional derivatives in systems with quintic nonlinearity
2022
AbstractWe study theoretically the properties of a soliton solution of the fractional Schrödinger equation with quintic nonlinearity. Under “fractional” we understand the Schrödinger equation, where ordinary Laplacian (second spatial derivative in 1D) is substituted by its fractional counterpart with Lévy index $$\alpha$$ α . We speculate that the latter substitution corresponds to phenomenological account for disorder in a system. Using analytical (variational and perturbative) and numerical arguments, we have shown that while in the case of Schrödinger equation with the ordinary Laplacian (corresponding to Lévy index $$\alpha =2$$ α = 2 ), the soliton is unstable, even infinitesimal diffe…
Effect of the Converging Pipe on the Performance of a Lucid Spherical Rotor
2018
Lucid spherical rotor is a cross-flow rotor developed to be installed within a pipeline. The purpose of installing this type of rotor is to collect excess energy available in gravity-fed water pipelines. In order to enhance the efficiency of the rotor which is installed in a channel, this paper aims to study the performance of Lucid spherical rotor with converging pipe. Numerical investigations were carried out to analyze the effect of the converging pipe on the performance of the rotor. Numerical simulations have been carried out using the unsteady Reynolds-averaged Navier–Stokes equations in conjunction with the realizable $$k-{\varepsilon }$$ turbulence model. The validation of the numer…
Propagation, Stability and Interactions of Novel Three-Wave Parametric Solitons
2006
International audience; We found a new class of analytic soliton solutions that describe the parametric wave mixing of optical pulses in quadratic nonlinear crystals. We analyze the stability properties, interactions and collisions of these solitons.
The fifth order Peregrine breather and its eight-parameters deformations solutions of the NLS equation.
2013
We construct here explicitly new deformations of the Peregrine breather of order 5 with 8 real parameters. This gives new families of quasi-rational solutions of the NLS equation and thus one can describe in a more precise way the phenomena of appearance of multi rogue waves. With this method, we construct new patterns of different types of rogue waves. We get at the same time, the triangular configurations as well as rings isolated. Moreover, one sees appearing for certain values of the parameters, new configurations of concentric rings.
High-order harmonic generation in fullerenes using few- and multi-cycle pulses of different wavelengths
2012
We present the results of experimental and theoretical studies of high-order harmonic generation (HHG) in plasmas containing fullerenes using pulses of different duration and wavelength. We find that the harmonic cutoff is extended in the case of few-cycle pulses (3.5 fs, 29th harmonic) compared to longer laser pulses (40 fs, 25th harmonic) at the same intensity. Our studies also include HHG in fullerenes using 1300 and 780 nm multicycle (35 and 40 fs) pulses. For 1300 nm pulses, an extension of the harmonic cutoff to the 41st order was obtained, with a decrease in conversion efficiency that is consistent with theoretical predictions based on wave packet spreading for single atoms. Theoreti…