Optical-Stark Induced Distortions in Vortex Momentum Distributions of p-Orbital Electrons of Neon Atoms

Yufei He,Jiu Tang,Xin Ding,Guizhong Zhang,Jianquan Yao

doi:10.1109/jphot.2020.3037714

Abstract

We present results of numerical simulations on the photoelectron momentum distributions of the p-orbital electrons of neon atoms ionized by a pair of time-delayed and oppositely circularly polarized intense laser pulses. Deploying the strong-field theory, we can readily produce vortex-shaped momentum distributions. Similarity and disparity in the vortex patterns between the neon and hydrogen atoms are observed. The optical Stark effect is found to induce distortions in the vortex momentum distributions, which are quantitatively described by introducing several physical quantities. Among these quantities, the autocorrelation parameter turns out to be the most sensitive probe for extremely weak Stark effect. The nonlinear phase induced by the optical Stark effect deciphers the distortions of the vortex momentum distributions.

Highlights

In the field of atomic, molecular, and optical physics, strong laser pulses are exclusively deployed to induce ionization or dissociation, and either momentum or energy spectra are extensively used to investigate the microscopic processes [1]–[5]
In order to discuss the properties of the vortex momentum distributions of the ionized p-orbital electrons, we conduct similar simulation for the s-orbital electrons in neon
For theses s-orbital electrons, our results show that the number of the vortex arms in the momentum distributions is equal to the total number of photons required to over the ionization threshold

Summary

Introduction

In the field of atomic, molecular, and optical physics, strong laser pulses are exclusively deployed to induce ionization or dissociation, and either momentum or energy spectra are extensively used to investigate the microscopic processes [1]–[5]. Similar studies were reported: for molecular system, Yuan et al [19] theoretically studied the photoelectron spectra generated by bi-chromatic circularly polarized attosecond laser pulses in 2016 They found that counter-rotating pulses could produce spiral momentum patterns. Djiokap [20] numerically investigated the single ionization of helium atom by circularly polarized laser pulses in 2016 They discovered that vortex momentum distributions with zero-start, one-start, three-start, and four-start could appear. We investigate the optical-Stark effect in the neon atoms in order to interrogate its influence on the distortions of the vortex-shaped momentum patterns. We anticipate that our research outcome could shed light on further investigation on strong field processes of atoms in association with Stark influence

Experimental Details

Numerical Results and Discussion

Conclusion