A systematic construction of Gaussian basis sets for the description of laser field ionization and high-harmonic generation

TL;DR

This paper introduces a systematic method for constructing optimized Gaussian basis sets to accurately model electron dynamics in atoms and molecules under intense laser fields, improving computational efficiency for high-harmonic generation and ionization studies.

Contribution

It presents a novel systematic scheme for creating Gaussian basis sets tailored for excited and continuum states in laser-atom interactions, enhancing accuracy and efficiency.

Findings

The proposed basis sets accurately describe electron dynamics in strong laser fields.

Time-dependent configuration interaction calculations validate the effectiveness of the basis sets.

Comparison shows improved performance over previous Gaussian basis sets.

Abstract

A precise understanding of mechanisms governing the dynamics of electrons in atoms and molecules subjected to intense laser fields has a key importance for the description of attosecond processes such as the high-harmonic generation and ionization. From the theoretical point of view, this is still a challenging task, as new approaches to solve the time-dependent Schr\"odinger equation with both good accuracy and efficiency are still emerging. Until recently, the purely numerical methods of real-time propagation of the wavefunction using finite grids have been frequently and successfully used to capture the electron dynamics in small one- or two-electron systems. However, as the main focus of attoscience shifts toward many-electron systems, such techniques are no longer effective and need to be replaced by more approximate but computationally efficient ones. In this paper, we explore the increasingly popular method of expanding the wavefunction of the examined system into a linear combination of atomic orbitals and present a novel systematic scheme for constructing an optimal Gaussian basis set suitable for the description of excited and continuum atomic or molecular states. We analyze the performance of the proposed basis sets by carrying out a series of time-dependent configuration interaction calculations for the hydrogen atom in fields of intensity varying from $5 \times 10^{13}\:\rm W/cm^2$ to $5 \times 10^{14}\:\rm W/cm^2$. We also compare the results with the data obtained using Gaussian basis sets proposed previously by other authors.