Shortcomings of the Keldysh approximation

Journal Article · Thu Sep 01 04:00:00 EDT 1988 · Phys. Rev. A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.38.2682· OSTI ID:6952655

Milonni, P W

A simple derivation of the Keldysh amplitude for the ionization of an atom by a strong field is presented using a perturbation expansion in the binding potential. It is shown that the ''Keldysh approximation'' is questionable under conditions of strong ionization, when there is substantial probability of removing the electron from its initial bound state. This is consistent with published numerical studies based on model binding potentials. It is argued that the Keldysh amplitude is not gauge invariant in the usual sense, and that it is effectively canceled in a conventional gauge-invariant formulation of strong-field perturbation theory.

• Research Organization: Theoretical Division (T-12), Los Alamos National Laboratory, Los Alamos, New Mexico 87545
• OSTI ID: 6952655
• Journal Information: Phys. Rev. A; (United States), Journal Name: Phys. Rev. A; (United States) Vol. 38:5; ISSN PLRAA
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
AMPLITUDES
ATOMS
BINDING ENERGY
EMISSION
ENERGY
FIELD EMISSION
GAUGE INVARIANCE
HAMILTONIANS
INVARIANCE PRINCIPLES
MATHEMATICAL OPERATORS
PERTURBATION THEORY
QUANTUM OPERATORS
TRANSITION AMPLITUDES