Nuclear classical dynamics of H$_2$ in intense laser field

TL;DR

This paper investigates the pathways and regions involved in single and double ionization of H₂ under intense laser fields, and models the coupled electron-nuclear dynamics using classical and quantum equations across various wavelengths and intensities.

Contribution

It provides a detailed analysis of ionization pathways and regions, and introduces a combined classical-quantum approach to simulate H₂ dynamics in intense laser fields.

Findings

Identified two pathways for single ionization and four for double ionization.

Mapped regions of space related to ionization processes.

Compared nuclear dynamics with and without laser field, noting the absence of bond hardening.

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 Schr\"{o}dinger 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 ($5\times10^{14}$ $Wcm^{-2} $ and $ 5\times10^{15}$ $Wcm^{-2}$) 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 field, 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.