Quantum chaos in doubly excited states of He

It has been known that a He atom as a classical three-body system is chaotic. How does the classical chaos manifest itself in quantum mechanics? The experimental observations so far show that the energy spectra of He are very regular. We studied the signature of quantum chaos in helium atom by examining the nearest-neighbor spacing (NNS) distributions of the energy levels of doubly excited states in collaboration with Prof. C.D. Linfs group at Kansas State University. We showed that the NNS gradually varies from the regular Poisson distribution to the chaotic Wigner distribution as the excitation energy is increased toward the double ionization threshold. This is the first rigorous quantum calculations for the helium atom at such high doubly excited states.

Nearest-neighbor spacing (NNS) distributions for doubly excited states of He(1Se) for the energy range from I14 to I19.
The Poisson and Wigner distribusions are shown as the red and blue curves, respectively.


gSignature of chaos in high-lying doubly excited states of helium atomh
A.T. Le, T. Morishita, X.-M. Tong, and C.D. Lin,
Phys. Rev. A 72, 032511 (2005) (14 pages).

Toru Morishita, UEC