Correlated electron dynamics with time-dependent quantum Monte Carlo: three-dimensional helium

TL;DR

This paper applies a novel time-dependent quantum Monte Carlo method to three-dimensional helium atoms, accurately modeling correlated electron dynamics and ionization under electromagnetic fields, showing improved results over traditional methods.

Contribution

It demonstrates the effectiveness of the time-dependent quantum Monte Carlo approach for simulating correlated electron dynamics in 3D atoms under external fields.

Findings

Accurate ground state energies close to exact values.

Enhanced ionization due to electron-electron correlation.

Good agreement with traditional methods for uncorrelated electrons.

Abstract

Here the recently proposed time-dependent quantum Monte Carlo method is applied to three dimensional para- and ortho-helium atoms subjected to an external electromagnetic field with amplitude sufficient to cause significant ionization. By solving concurrently sets of up to 20 000 coupled 3D time-dependent Schroedinger equations for the guide waves and corresponding sets of first order equations of motion for the Monte Carlo walkers we obtain ground state energies in close agreement with the exact values. The combined use of spherical coordinates and B-splines along the radial coordinate proves to be especially accurate and efficient for such calculations. Our results for the dipole response and the ionization of an atom with un-correlated electrons are in good agreement with the predictions of the conventional time-dependent Hartree-Fock method while the calculations with correlated electrons show enhanced ionization that is due to the electron-electron repulsion.