Signature of chaos in high-lying doubly excited states of the helium atom

Journal Article · Thu Sep 15 04:00:00 EDT 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.72.032511· OSTI ID:20718537

Le, Anh-Thu; Tong, X -M; Lin, C D ^[1]; Morishita, Toru ^[2]

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1. Department of Physics, Cardwell Hall, Kansas State University, Manhattan, Kansas 66506 (United States)
2. Department of Applied Physics and Chemistry, University of Electro-Communications 1-5-1 Chofu-ga-oka, Chofu-shi, Tokyo 182-8585 (Japan)

We examined nearest-neighbor spacing (NNS) statistics in doubly excited states of helium near the double ionization threshold. Using the Brody parameter q to measure the NNS distribution between the regular Poisson distribution (q=0) and the chaotic Wigner distribution (q=1), we showed that for levels near the N=20 threshold of He{sup +}, or at about 0.13 eV below the double ionization threshold, the NNS distribution has q=0.66. The result shows the slow approach of the NNS of helium energy levels towards the Wigner distribution vs the excitation energy. Using an s-wave model where the angular momentum of each electron is restricted to zero, we also examined the NNS for levels up to the N=30 threshold of He{sup +}. We showed the gradual increase in q as the excitation energy is increased. To generate the theoretical data needed for the NNS analysis, we have used the hyperspherical close-coupling method, with the recently proposed diabatization of potential curves and the truncation of channels, to greatly reduce the complexity in the calculation. We also investigated the dependence of q vs the nuclear charge in the same scaled energy region, and for different symmetries, to assess their relation with the rate of approaching the q=1 Wigner distribution.

• OSTI ID: 20718537
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 3 Vol. 72; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ANGULAR MOMENTUM
ATOMS
CATIONS
CHAOS THEORY
COUPLING
DISTRIBUTION
ELECTRONS
EV RANGE
EXCITATION
EXCITED STATES
HELIUM
HELIUM IONS
POTENTIAL ENERGY
POTENTIALS
S WAVES
SURFACE IONIZATION
SYMMETRY
WIGNER DISTRIBUTION