Spin dynamics of wave packets evolving with the Dirac Hamiltonian in   atoms with high Z
  The motion of circular WP for one electron in central Coulomb field with high Z is calculated. The WP is defined in terms of solutions of the Dirac equation in order to take into account all possible relevant effects in particular the spin-orbit potential. A time scale is defined within which spin dynamics must be taken into account mainly in the atoms with high Z. Within this time scale there exists a mechanism of collapses and revivals of the spin already shown by the authors for harmonic oscillator potential and called the 'spin-orbit pendulum'. However this effect has not the exact periodicity of the simpler model, but the WP's spatial motion is nevertheless quite similar. 
R.Arvieu (ISN, Grenoble, France), P.Rozmej and M.Turek (University   MCS, Lublin, Poland)