Accurate computation of above threshold ionization spectra for stretched ${{\rm{H}}}_{2}^{+}$ in strong laser fields

Abstract

Investigations on the simplest benchmark system can reveal most underlying mechanisms for the intricate dynamics of molecular systems induced by strong laser pulses. However, due to the two-center Coulomb potential and the highly nonlinear nature of the electron dynamics, the accurate computation of the above threshold ionization spectra remains challenging, especially at large internuclear distances and high laser intensities. In the present work, we implement a new Gauss-quadrature approximation (GA) in the framework of finite element discrete variable representation to solve the time-dependent Schrödinger equation of in strong laser fields. By using this GA, one can arrive at a matrix representation of the first derivative operator that keeps its anti-hermiticity. This crucial feature allows a very stable propagation of the wavefunction under the usual Lanczos scheme. Combining with a wavefunction splitting in the asymptotic region, we show that our present numerical method can reliably deal with the electronic dynamics of stretched molecules at large internuclear distances for high laser intensities and long pulse durations. Accurate photoelectron momentum distributions under these conditions are presented and the distinct features due to the two-center potential are discussed.

Photon-momentum transfer in diatomic molecules: An ab initio study

“…In this work, we adopt such a gauge that the electric quadrupole term and the magnetic dipole term is separate and explicitly expressed. The resultant TDSE is solved at the fixed nuclear approximation in the prolate spheroidal coordinates using similar methods to those previously used for the dipole case [53][54][55].…”

Nondipole effects in interference patterns of a two-electron wave

“…With the internuclear distance R fixed at R e = 1.4 a.u., we expand the electronic wave function in prolate spheroidal coordinates (ξ, η, φ) with a production basis of the finite element discrete variable representation [11] and spherical harmonics. After discretization, one can search for the ground state |0 of the field free Hamiltonian H 0 of H 2 with the restarted Lanczos scheme and then propagate (i∂ t − H 0 ) |ψ = H int |0 in time with the short-time Arnoldi propagator [12]. Specific forms of each term in the Hamiltonian can be found in Refs.…”

Controlling quantum wave packet of electronic motion on field‐dressed Coulomb potential of by carrier‐envelope phase‐dependent strong field laser pulses

“…Thus as increases and the orbitals are distorted, its Coulomb potential and the laser field form the inner barrier to further ionize . This important nonlinear effect is a result of interference of two lowest states leading to charge resonance enhanced ionization [50, 51]. For the strong‐field ionization of such two‐center molecule consisting of two Coulomb potential wells, the two most important orbitals could be the highest occupied molecular orbital (HOMO) or the lowest unoccupied molecular orbital (LUMO).…”

“…Since the barrier height separating the two wells increases considerably, the electron gets trapped, ending its route in the upper potential well. This leads to electron localization and thus dissociative‐ionization, and acts as well as the trigger of charge resonance enhanced ionization [50, 51]. Conversely, the Coulomb potentials for ϑ = 180°−200° distort in such a way that the becomes LUMO and becomes HOMO as separation increases and enhances the opposite mechanism of electron localization being preferentially on the left proton.…”