Scaling laws for the photo-ionisation cross section of two-electron atoms

Abstract

The cross sections for single-electron photo-ionisation in two-electron atoms show fluctuations which decrease in amplitude when approaching the double-ionisation threshold. Based on semiclassical closed orbit theory, we show that the algebraic decay of the fluctuations can be characterised in terms of a threshold law $\sigma \propto |E{|}^{\mu }$ as $E\to 0_{-}$ with exponent $\mu$ obtained as a combination of stability exponents of the triple-collision singularity. It differs from Wannier's exponent dominating double ionisation processes. The details of the fluctuations are linked to a set of infinitely unstable classical orbits starting and ending in the non-regularisable triple collision. The findings are compared with quantum calculations for a model system, namely collinear helium.

arXiv comment4 pages, 1 figure

References in corpus (4)

• General Quantum Surface of Section Method
• Semiclassical quantization of the hydrogen atom in crossed electric and magnetic fields
• Classical dynamics near the triple collision in a three-body Coulomb problem
• The classical dynamics of two-electron atoms near the triple collision

Cited by in corpus (5)

• Essential entanglement for atomic and molecular physics
• Initial state dependence in multi-electron threshold ionization of atoms
• Evidence of triple collision dynamics in partial photo-ionisation cross sections of helium
• Extracting partial decay rates of helium from complex rotation: autoionizing resonances of the one-dimensional configurations
• Classical Mechanics of Collinear Positron-Hydrogen Scattering