Highly ionized xenon and volumetric weighting in restricted focal geometries

TL;DR

This study investigates highly ionized xenon atoms under ultrafast laser pulses, analyzing ion yields and spatial averaging effects to improve interpretation of experimental data.

Contribution

It introduces a hybrid analytical-numerical method to account for spatial averaging in restricted focal geometries during xenon ionization experiments.

Findings

Observed sequential and nonsequential ionization structures.

Achieved agreement between experimental data and simulations.

Highlighted importance of spatial averaging correction in experiments.

Abstract

The ionization of xenon atoms subjected to 42fs, 800nm pulses of radiation from a Ti:Sapphire laser was investigated. In our experiments a maximum laser intensity of $\sim2\times 10^{15} \textrm{W}/\textrm{cm}^2$ was used. Xenon ions were measured using a time-of-flight ion mass spectrometer having an entrance slit with dimensions of $12\mu \textrm{m} \times 400\mu \textrm{m}$. The observed yields $\textrm{Xe}^{n+} (n=1-7)$ were partially free of spatial averaging. The ion yields showed sequential and nonsequential multiple ionization and dip structures following saturation. To investigate the dip structures and to perform a comparison between experimental and simulated data, with the goal of clarifying the effects of residual spatial averaging, we derived a hybrid analytical-numerical solution for the integration kernel in restricted focal geometries. We simulated xenon ionization using Ammosov-Delone-Krainov and Perelomov-Popov-Terent'ev theories and obtained agreement with the results of observations. Since a large number of experiments suffer from spatial averaging, the results presented are important to correctly interpret experimental data by taking into account spatial averaging.