arXiv subjects

A. Maghari

Publications and source records attributed to A. Maghari.

3 recordsLinked to original sources

arXiv2016

Identifying spatially asymmetric high-order harmonic emission during the falling edge of an intense laser pulse

Two different induced effects of a laser falling edge on high-order harmonic generation are resolved by solving numerically full-dimensional electronic time-dependent Schrödinger equation beyond the Born-Oppenheimer approximation. The harmonic spectrum of H$_2^+$ and T$_2^+$ isotopes are compared to see the effects of a 4-cycle falling edge of a 800 nm, 15-cycle trapezoidal laser pulse of $I=$3 $\times 10^{14}$ Wcm$^{-2}$ intensity on harmonic emission spectrum. The harmonic emission at the laser falling part is negligible for H$_2^+$ due to ionization suppression, but considerable for T$_2^+$. The falling edge of the laser pulse induces two effects on the HHG in T$_2^+$. The first well-known effect is non-adiabatic frequency redshift of generated odd-order harmonics. The second unknown one is spatially asymmetric harmonic emission which appears as even harmonic orders. In order to clarify this new effect, spatial distribution of HHG and resolving HHG into different components are demonstrated. The asymmetric emission would appear for both atoms and molecules as long as harmonic emission of either rising or falling edge of an intense trapezoidal or non-trapezoidal laser pulse is dominant.

physics.atom-ph↗

arXiv2016

Understanding molecular harmonic emission at relatively long intense laser pulses: Beyond the Born-Oppenheimer approximation

The underlying physics behind the molecular harmonic emission in relatively long sin$^2$-like laser pulses is investigated. We numerically solved the full-dimensional electronic time-dependent Schrödinger equation beyond the Born-Oppenheimer approximation for simple molecular ion H$_2^+$. The occurrence and the effect of electron localization, non-adiabatic redshift and spatially asymmetric emission are evaluated to understand better complex patterns appearing in the high-order harmonic generation (HHG) spectrum. Results show that the complex patterns in the HHG spectrum originate mainly from a non-adiabatic response of the molecule to the rapidly changing laser field and also from a spatially asymmetric emission along the polarization direction. The effect of electron localization on the HHG spectrum was not observed as opposed to what is reported in the literature.

physics.atom-ph↗

arXiv2015

Complicated high-order harmonic generation due to the falling edge of a trapezoidal laser pulse

High-order harmonic generation (HHG) is investigated for H$_2^+$ and its isotopomers under seven- and ten-cycle trapezoidal laser pulses at 800 nm wavelength and $I$=4$\times 10^{14}$ W$/$cm$^2$ intensity. We solved numerically full-dimensional electronic time-dependent Schrödinger equation with and without the Born-Oppenheimer approximation. We show that the HHG at the falling edge of a trapezoidal laser pulse can result in redshift and complexity on the total HHG spectrum which can be removed by considering different laser pulse duration and nuclear motion not possible for sin$^2$ and Gaussian laser pulses. We resolve the redshifts and complexities of the HHG spectra into different electronic and vibrational states and their interferences.

physics.atom-ph↗