Helium atom as a classical three-body problem

The classical three-body problem of the helium atom is numerically studied. For most initial conditions, orbits show chaotic transients until one of the electrons always escapes to infinity, leading to autoionization. For the remaining parts of initial conditions, several types of stable quasiperiodic motions (on tori) are found, which have a finite measure in the phase space. This discovery enables us to treat semiclassically a strongly correlated electronic system.