Nuclear classical dynamics of H₂in an intense laser field

Abstract

In the first part of this paper, the different distinguishable pathways and regions of the single and sequential double ionization are determined and discussed. It is shown that there are two distinguishable pathways for the single ionization and four distinct pathways for the sequential double ionization. It is also shown that there are two and three different regions of space which are related to the single and double ionization respectively. In the second part of the paper, the time dependent Schrödinger and Newton equations are solved simultaneously for the electrons and the nuclei of H 2 respectively. The electrons and nuclei dynamics are separated on the base of the adiabatic approximation. The soft-core potential is used to model the electrostatic interaction between the electrons and the nuclei. A variety of wavelengths (390 nm, 532 nm and 780 nm) and intensities ( 5 × 10 14 W cm −2 and 5 × 10 15 W cm −2 ) of the ultrashort intense laser pulses with a sinus second order envelope function are used. The behaviour of the time dependent classical nuclear dynamics in the absence and present of the laser field are investigated and compared. In the absence of the laser eld, there are three distinct sections for the nuclear dynamics on the electronic ground state energy curve. The bond hardening phenomenon does not appear in this classical nuclear dynamics simulation.

High harmonic generation from pre-ionized H2in ultrashort intense laser fields

“…[25]). In order to simplify the numerical solution of the electron-nuclear TDSE within the adiabatic approximation [27] a semiclassical approach has been adopted to calculate the instantaneous forces applied on each nucleus by the other, the evolving electronic wavepacket and the laser field [24,27]. The instantaneous positions of the nuclei needed for the evaluation of the forces are calculated based on the Verlet algorithm [30].…”

“…The temporal evolution of electrons of this system is described by the time dependent Schrödinger equation (TDSE), i.e. [24,27] …”

“…The details of the numerical simulation is presented in Ref. [24] u., respectively) are used. For all cases, a pulse shape of ε(t) = E 0 sin 2 (tπ/τ ) cos(ωt) is used for the electric field of the laser, and the pulse length is set to τ =8 cycles, along with a fixed time step of t = 0.02.…”

Mapping electron dynamics in molecular H2using high-order-harmonic-generation time profiles

“…Special attention is paid to the dynamics of the isolated homolytic and ionic doorways or transient species produced during the evolution of the two-electron wave packet of H 2 based on the three alternative forms of HHG spectra, including position r , velocity ṙ , and acceleration r moments, all [38,44], adopted for the study of preionization transient species in the interaction of the 1D twoelectron H 2 system with ultrashort intense laser pulses. The two (green) dots near the origin represent initial positions of the two H nuclei located symmetrically around the origin (with a 2.13 distance to each other).…”

“…In the past decade, numerous attempts at monitoring electronic dynamics and investigating the detailed structure of the ionization rates and enhanced ionization have been made on the dynamics of the bound electron in the one-electron H + 2 molecular system [31][32][33][34][35]. However, only a limited number of works have been devoted to the mechanism of the intramolecular two-electron dynamics induced by an intense laser field [36][37][38].…”