SLIMP 2.0: A new version of strong laser interaction model package for atoms and molecules, now with molecular orbital tomography based on high-order harmonic spectra

Abstract

A new version of strong laser interaction model package for atoms and molecules is presented. Its capacities are enhanced by incorporating modules related to molecular orbital tomography (MOT) in length and velocity forms based on high-order harmonic spectra (HHS). This advanced package enables two-dimensional and three-dimensional MOT of both symmetric and asymmetric molecules using HHS, providing an efficient means for both experimental and theoretical investigations of molecular orbital structures. In addition, it can calculate the precise theoretical orbitals corresponding to those reconstructed by MOT. Furthermore, the package can calculate the transition dipole moment (TDM) in the plane wave approximation and allow for reference MOT based on TDM. It can evaluate the quality of reconstructed orbitals based on HHS and reveal the physical and numerical effects on MOT. This package is suitable for MOT under conditions of driving laser at different intensities and wavelengths, and can be applied to different molecules with various structures. It is designed to facilitate easy expansion for additional capabilities. Program summaryProgram Title: SLIMP, version 2.0CPC Library link to program files:https://doi.org/10.17632/jgcb7m7wwv.1Licensing provisions: GPLv3Programming language: Fortran 90Journal reference of previous version: Comput. Phys. Commun. 192 (2015) 330-341.Does the new version supersede the previous version?: Yes.Reasons for the new version: Molecular orbital tomography (MOT) [1] based on high-order harmonic spectra (HHS) [2] is an important research topic in the field of strong-field physics. It provides an efficient way to probe molecular orbital structures experimentally, which was not considered in the former version of SLIMP [3] and is now included in SLIMP 2.0. The new version package allows performing two-dimensional (2D) and three-dimensional (3D) MOT [4] based on HHS obtained from experiments or simulations, providing reliable detections for many orbitals of interest, either symmetric or asymmetric molecules.Summary of revisions: Extending capacities focus on enabling performing 2D and 3D MOT on symmetric and asymmetric molecules based on HHS, and together the relevantly precise theoretical orbital output, calculation of transition dipole moment (TDM) and reference MOT based on TDM. For 2D MOT, MOT in both length and velocity forms are implemented.Nature of problem: To perform MOT based on HHS, the user needs general reconstruction programs, taking symmetric and asymmetric molecules, 2D and 3D orbitals, and MOT in length and velocity forms into account. In addition, evaluation of imaging quality is required, which can reveal the physical and numerical effects on reconstructions.Solution method: The 2D symmetric and asymmetric, length- and velocity-form, and 3D reconstruction algorithms are implemented based on Fortran 90. Furthermore, this package provides a reference MOT based on directly calculated TDM, served as a comparable result to the reconstructed orbital based on HHS. The comparison between reconstructions based on HHS and TDM can reveal the effects on MOT in physical and numerical aspects.Additional comments including restrictions and unusual features: This package does not include MOT of asymmetric molecules in velocity form. For the 2D MOT based on HHS, the reconstructed 2D projection of gerade, ungerade orbital or the gerade and ungerade components of asymmetric orbital must have the axial symmetry about the x- and z-axis. For the 3D MOT, the reconstructed 3D orbital has to be cylindrically symmetric.