Evidence of triple collision dynamics in partial photo-ionisation cross sections of helium

TL;DR

This paper demonstrates that partial photo-ionisation cross sections of helium are governed by triple collision dynamics, confirming recent semiclassical predictions and explaining observed self-similar structures in experimental data.

Contribution

It develops a modified semiclassical theory for partial cross sections and validates it through experimental data analysis, confirming the role of triple collision dynamics.

Findings

Partial cross sections are dominated by triple collision dynamics.

Fourier analysis of experimental data reveals semiclassical contributions.

The results confirm the validity of recent theoretical predictions.

Abstract

Experimental results on partial photo-ionisation cross sections of helium are analysed in the light of recent advances in the semiclassical theory of two-electron atoms. Byun et al (arXiv:physics/0701086) predict that the total photo-ionisation cross section below the double-ionisation threshold can, semiclassically, be described in terms of contributions associated with classical orbits starting and ending in the triple collision. The necessary modifications of the semiclassical theory for partial cross sections is developed here. It is argued that partial cross sections are also dominated by the triple collision dynamics. The expected semiclassical contributions can be identified in the Fourier transformation of the experimental data. This clearly demonstrates for the first time the validity of the basic assumptions made in Byun et al. Our findings explain furthermore in a natural way the self-similar structures observed in cross section signals for different channel numbers.