2007/01/08 by Chang Woo Byun, Nark Nyul Choi, Min-Ho Lee +1 · 1 citation
Physics and Astronomy · #Advanced Chemical Physics Studies #Amplitude #Atomic and Molecular Physics #Atomic physics #Double ionization #Electron #Exponent #Helium #Ion #Ionization #Photoionization #Physics #Quantum #Quantum mechanics #Scaling #Semiclassical physics #Singularity #Spectroscopy and Quantum Chemical Studies #nlin.CD #physics.atom-ph
paper · pdf · doi:10.1103/physrevlett.98.113001
published as Phys Rev Lett 98, 113001 (2007) · 4 pages, 1 figure
arxiv created 2007/01/08 · openalex publication_date 2007/03/14 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The cross sections for single-electron photoionization in two-electron atoms show fluctuations which decrease in amplitude when approaching the double-ionization threshold. Based on semiclassical closed orbit theory, we show that the algebraic decay of the fluctuations can be characterized in terms of a threshold law sigma proportional to |E|(mu) as E --> 0(-) with exponent mu obtained as a combination of stability exponents of the triple-collision singularity. It differs from Wannier's exponent dominating double-ionization processes. The details of the fluctuations are linked to a set of infinitely unstable classical orbits starting and ending in the nonregularizable triple collision. The findings are compared with quantum calculations for a model system, namely, collinear helium.