Search results for "harmonics"
showing 10 items of 199 documents
Small Angular Scale Simulations of the Microwave Sky
1996
We describe and compare two types of microwave sky simulations which are good for small angular scales. The first type uses expansions in spherical harmonics, and the second one is based on plane waves and the Fast Fourier Transform. The angular power spectrum is extracted from maps corresponding to both types of simulations, and the resulting spectra are appropriately compared. In this way, the features and usefulness of Fourier simulations are pointed out. For $\ell \geq 100$, all the simulations lead to similar accuracies; however, the CPU cost of Fourier simulations is $\sim 10$ times smaller than that for spherical harmonic simulations. For $\ell \leq 100$, the simulations based on sph…
Comments on “Four-Stream Spherical Harmonic Expansion Approximation for Solar Radiative Transfer”
1998
Comments on : four-stream spherical harmonic expansion approximation for solar radiative transfer.
Comparison of cartesian and lobe function Gaussian basis sets
1970
The lobe function and cartesian (spherical harmonic) gaussian are compared with reference to calculations for second-row atoms. Single and grouped gaussian basis sets which have been reported for cartesian functions are taken over directly to construct corresponding lobe function bases with identical sets of exponents and with lobe separations chosen by a scaling procedure. Total and orbital energies and SCF coefficients resulting from calculations on the second-row atoms using the two types of functions for both primitive and grouped gaussian basis sets are seen to be in excellent agreement, thereby emphasizing the essential equivalence of lobe functions and cartesian gaussians, at the ver…
Effective field analysis using the full angular spin-orbit torque magnetometry dependence
2017
Spin-orbit torques promise ultra-efficient magnetization switching used for advanced devices based on emergent quasi-particles such as domain walls and skyrmions. Recently, the spin structure dynamics, materials and systems with tailored spin-orbit torques are being developed. A method, which allows one to detect the acting torques in a given system as a function of the magnetization direction is the torque-magnetometry method based on a higher harmonics analysis of the anomalous Hall-effect. Here we show that the effective fields acting on magnetic domain walls that govern the efficiency of their dynamics require a sophisticated analysis taking into account the full angular dependence of t…
High-order harmonic emission from a three-level atom in a laser field
1999
Abstract The spectrum emitted by a three-level atom in the presence of a weak laser field is given together with the population dynamics and the phase of the Fourier transform of the acceleration. Calculations show that the spectrum can be very different from that emitted by a two-level atom. When the trapping conditions are obtained, the coupling to the third level can result in a large change in the spectrum.
Electromagnetic scattering by a strip grating with nonplanar illumination
1993
An angular-spectrum method combined with the Galerkin procedure has been used to evaluate the electromagnetic scattering of a beam radiated by an aperture antenna after being incident obliquely upon a strip grating. Integral expressions for the transmitted and reflected fields are obtained. The incident beam radiated by the antenna is diffracted in several beams corresponding to the propagative Floquet harmonics. An angular shift of the transmitted and reflected fundamental harmonic beams has been shown. Comparison between numerical and experimental results validates this method. © 1993 John Wiley & Sons, Inc.
Even harmonics from laser driven homonuclear molecules
2007
The dynamics of a homonuclear diatomic molecule driven by a laser pulse is obtained beyond the fixed nuclei approximation. Laser parameters can be adjusted to confine the electron over one of the two nuclei for a relatively long time or not. A time-resolved analysis of the electromagnetic spectrum emitted by the molecule presents the usual odd harmonics far from confinement and even harmonics during the confinement periods. A physical interpretation of the results is given.
High Order Harmonics from a Molecule: Evidence of the Nuclear Motion
2007
The electromagnetic spectrum emitted by a molecule driven by a laser presents harmonics and satellite lines whose separation is equal to the oscillation frequency of the nuclei. Full quantum and semiclassical calculations are presented.
Higher-order Kerr effects improve quantitative modelling of harmonics generation and laser filamentation
2013
The consideration of the higher-order Kerr effect (HOKE) drastically improves the quantitative agreement between measured and simulated harmonic yield as well as intensity and electron density in laser filaments generated by pulses below a few hundreds of fs. In longer pulses, the plasma defocusing plays a much more important role.
Plasma radiation spectra in the presence of static electric and high-frequency radiation fields
2004
Harmonics generation of high-frequency radiation in a plasma embedded in a constant electric field is investigated theoretically. It is shown that the electron directed motion due to the static electric field yields the appearance in the plasma emission spectrum of high-frequency radiation even harmonics. The conditions are established when the even harmonics generation is as effective as that of the odd ones. At variance with the odd harmonics, the even harmonics polarization plane is found to rotate with respect to that of the fundamental field. The basic dependencies concerning the rotation angle and the generation efficiency on the plasma and field parameters are established.