Molecular photoelectron angular distribution rotations in multi-photon resonant ionization of H2+ by circularly polarized ultraviolet laser pulses

Abstract

We study effects of pulse durations on molecular photoelectron angular distributions (MPADs) in ultrafast circular polarization ultraviolet resonant ionization processes. Simulations performed on aligned H2 (+) by numerically solving time dependent Schrödinger equations show rotations of MPADs with respect to the molecular symmetry axes. It is found that in multi-photon resonant ionization processes, rotation angles are sensitive to pulse durations, which we attribute to the coherent resonant excitation between the ground state and the intermediate excited electronic state induced by Rabi oscillations. Multi-photon nonresonant and single photon ionization processes are simulated and compared which exhibit a constant rotation angle. An asymmetry parameter is introduced to describe the pulse duration sensitivity by perturbation theory models. Influence of pulse frequency detunings on MPADs is also investigated where oscillations of rotations are absent at long pulse durations due to nonresonance excitation.

Attosecond Dynamics of Molecular Electronic Ring Currents

“…37,38 For intense high-frequency laser pulses, a quite large grid range must be used to obtain via Fourier transforming the high energy of the ejected electron in the ionization spectra. In this work, we calculate molecular-frame photoelectron angular distributions at the kinetic energy E by a Fourier transformation of the time-dependent electronic flux as 39,40 ∫ ∫…”

“…We numerically solve the TDSE by using a five-point finite difference method and fast Fourier transform technique combined with high-order split-operator methods. , For intense high-frequency laser pulses, a quite large grid range must be used to obtain via Fourier transforming the high energy of the ejected electron in the ionization spectra. In this work, we calculate molecular-frame photoelectron angular distributions at the kinetic energy E by a Fourier transformation of the time-dependent electronic flux as , where ρ i is an asymptotic point before the electronic wave packet is absorbed at the grid boundary and t p is the time after the probe pulse turns off. From the relation between the kinetic energy E and the momentum p with E = p 2 /2 and transformation between the cylindrical (ρ, θ) and Cartesian ( x , y ) with p x = p cos θ and p y = p sin θ, we obtain the 2D momentum distribution spectrum of the photoelectron.…”

Nonlinear Nonperturbative Optics Model Enriched by Evolution Equation for Polarization

“…Although in its whole generality the MASP model for H + 2 includes the motion of the 3 particles [28], we will use the Born-Oppenheimer approximation throughout the article. It is a typical approximation in quantum chemistry, since the time-scale for dynamics of the interatomic electrons (attoseconds) is much shorter then the timescale for the nuclei motion (femtoseconds) [14,37,50]. At the molecular (microscopic) scale, we will denote by x = (x, y, z) T the TDSEs space variable (that is for electron wavefunctions).…”

Toward the Full Quantum Dynamical Description of Photon Induced Processes in D2+

“…Accordingly, they have been the subject of many theoretical and experimental studies for more than quarter of a century. Most of these works concentrated on the photodissociation and ionization of the molecule. − These processes are usually investigated through either the nuclear kinetic energy release (KER) spectra or the photoelectron energy spectrum. Among others it was pointed out that deeper insight may be obtained from the joint energy spectrum (JES), where electrons and ions are measured in coincidence.…”