Computing Classical Escape Rates from Periodic Orbits in Chaotic Hydrogen

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Main Authors: Custodio, Ethan T., Sattari, Sulimon, Mitchell, Kevin A.
Format: Preprint
Published: 2025
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author Custodio, Ethan T.
Sattari, Sulimon
Mitchell, Kevin A.
author_facet Custodio, Ethan T.
Sattari, Sulimon
Mitchell, Kevin A.
contents When placed in parallel magnetic and electric fields, the electron trajectories of a classical hydrogen atom are chaotic. The classical escape rate of such a system can be computed with classical trajectory Monte Carlo techniques, but these computations require enormous numbers of trajectories, provide little understanding of the dynamical mechanisms involved, and must be completely rerun for any change of system parameter, no matter how small. We demonstrate an alternative technique to classical trajectory Monte Carlo computations, based on classical periodic orbit theory. In this technique, escape rates are computed from a relatively modest number (a few thousand) of periodic orbits of the system. One only needs the orbits' periods and stability eigenvalues. A major advantage of this approach is that one does not need to repeat the entire analysis from scratch as system parameters are varied; one can numerically continue the periodic orbits instead. We demonstrate the periodic orbit technique for the ionization of a hydrogen atom in applied parallel electric and magnetic fields. Using fundamental theories of phase space geometry, we also show how to generate nontrivial symbolic dynamics for acquiring periodic orbits in physical systems. A detailed analysis of heteroclinic tangles and how they relate to bifurcations in periodic orbits is also presented.
format Preprint
id arxiv_https___arxiv_org_abs_2503_15710
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Computing Classical Escape Rates from Periodic Orbits in Chaotic Hydrogen
Custodio, Ethan T.
Sattari, Sulimon
Mitchell, Kevin A.
Chaotic Dynamics
Atomic Physics
When placed in parallel magnetic and electric fields, the electron trajectories of a classical hydrogen atom are chaotic. The classical escape rate of such a system can be computed with classical trajectory Monte Carlo techniques, but these computations require enormous numbers of trajectories, provide little understanding of the dynamical mechanisms involved, and must be completely rerun for any change of system parameter, no matter how small. We demonstrate an alternative technique to classical trajectory Monte Carlo computations, based on classical periodic orbit theory. In this technique, escape rates are computed from a relatively modest number (a few thousand) of periodic orbits of the system. One only needs the orbits' periods and stability eigenvalues. A major advantage of this approach is that one does not need to repeat the entire analysis from scratch as system parameters are varied; one can numerically continue the periodic orbits instead. We demonstrate the periodic orbit technique for the ionization of a hydrogen atom in applied parallel electric and magnetic fields. Using fundamental theories of phase space geometry, we also show how to generate nontrivial symbolic dynamics for acquiring periodic orbits in physical systems. A detailed analysis of heteroclinic tangles and how they relate to bifurcations in periodic orbits is also presented.
title Computing Classical Escape Rates from Periodic Orbits in Chaotic Hydrogen
topic Chaotic Dynamics
Atomic Physics
url https://arxiv.org/abs/2503.15710