# Atomic and Molecular Processes in a Strong Bicircular Laser Field

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## Abstract

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## 1. Introduction: Three-Step Model and Bicircular Laser Field

## 2. Results for High-Order Harmonic Generation by Bicircular Field

## 3. Spin Asymmetry in Above-Threshold Ionization by Bicircular Field

## 4. Conclusions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**Graphical sketch of the three-step model for high-order harmonic generation. The combined atomic and laser field potential is presented by black lines, while the electron and its velocity are shown in blue. The temporal evolution of a linearly polarized laser field ${E}_{\mathrm{lin}}\left(t\right)$ is depicted by the red long-dashed line. The emitted high-harmonic photon is illustrated by a pink wavy line with an arrow at the end.

**Figure 2.**The electric-field-vector polar diagram for the $r\omega $–$s\omega $ bicircular field, having equal component intensities, plotted for $0\le t\le T=2\pi /\omega $, with the fundamental frequency $\omega $. The six presented panels depict the field for various combinations of the values of r and s, as denoted.

**Figure 3.**Three-dimensional graphs of the logarithm of the harmonic emission rate as a function of the harmonic order and laser intensity (in atomic units). Upper panel (

**a**): Linearly polarized laser field. Lower panel (

**b**): $\omega $–$2\omega $ bicircular laser field. The fundamental photon energy is $\omega =1.6$ eV and Ar atoms are modeled by s ground state. The same arbitrary units for HHG rates are used in both panels.

**Figure 4.**Focal-averaged results for Xe atoms ionized by $\omega $–$2\omega $ bicircular field with the fundamental wavelength 800 nm and the same component peak intensities ${I}_{1}={I}_{2}=1.1\times {10}^{14}\phantom{\rule{0.277778em}{0ex}}\mathrm{W}/{\mathrm{cm}}^{2}$, depicted in false colors in the photoelectron momentum plane. Top panels (

**a**,

**b**): The logarithm of the summed photoelectron yield ${W}_{\mathbf{p}\uparrow}+{W}_{\mathbf{p}\downarrow}$. Middle panels (

**c**,

**d**): Normalized spin asymmetry parameter ${\tilde{A}}_{\mathbf{p}}$. Bottom panels (

**e**,

**f**): Spin asymmetry parameter ${A}_{\mathbf{p}}$. Left panels (

**a**,

**c**,

**e**): Only the direct electrons are taken into account. Right panels (

**b**,

**d**,

**f**): Only the rescattered electrons are accounted for.

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**MDPI and ACS Style**

Milošević, D.B.
Atomic and Molecular Processes in a Strong Bicircular Laser Field. *Atoms* **2018**, *6*, 61.
https://doi.org/10.3390/atoms6040061

**AMA Style**

Milošević DB.
Atomic and Molecular Processes in a Strong Bicircular Laser Field. *Atoms*. 2018; 6(4):61.
https://doi.org/10.3390/atoms6040061

**Chicago/Turabian Style**

Milošević, Dejan B.
2018. "Atomic and Molecular Processes in a Strong Bicircular Laser Field" *Atoms* 6, no. 4: 61.
https://doi.org/10.3390/atoms6040061