Electron momentum distributions and photoelectron spectra of atoms driven by intense spatially inhomogeneous field

TL;DR

This study uses 3D--TDSE calculations to explore how spatially inhomogeneous laser fields affect electron momentum distributions and photoelectron spectra in atoms, revealing significant effects in tunneling ionization and potential for high-energy electron generation.

Contribution

It demonstrates the impact of inhomogeneous fields on ATI processes and electron energies, highlighting effects in tunneling regimes and the influence of carrier envelope phase.

Findings

Inhomogeneous fields cause significant modifications in tunneling ionization.

Electrons can reach near-keV energies in mid-$10^{14}$ W/cm$^{2}$ fields.

Carrier envelope phase affects ATI photoelectron emission in few-cycle pulses.

Abstract

We use three dimensional time-dependent Schr\"odinger equation (3D--TDSE) to calculate angular electron momentum distributions and photoelectron spectra of atoms driven by spatially inhomogeneous fields. An example for such inhomogeneous fields is the locally enhanced field induced by resonant plasmons, appearing at surfaces of metallic nanoparticles, nanotips and gold bow-tie shape nanostructures. Our studies show that the inhomogeneity of the laser electric field plays an important role in the above threshold ionization process in the tunneling regime, causing significant modifications to the electron momentum distributions and photoelectron spectra, while its effects in the multiphoton regime appear to be negligible. Indeed, through tunneling ATI process, one can obtain higher energy electrons as well as high degree of asymmetry in the momentum space map. In this study we consider near infrared laser fields with intensities in the mid-$10^{14}$ W/cm$^{2}$ range and we use linear approximation to describe their spatial dependence. We show that in this case it is possible to drive electrons with energies in the near-keV regime. Furthermore, we study how the carrier envelope phase influences the emission of ATI photoelectrons for few-cycle pulses. Our quantum mechanical calculations are fully supported by their classical counterparts.