Effect of a strong laser on spin precession

The semiclassical dynamics of a charged spin-1/2 particle in an intense electromagnetic plane wave is analyzed beyond the electric dipole approximation and taking into account the leading relativistic corrections to the Pauli equation. It is argued that the adiabatic spin evolution driven by a low intensity radiation changes its character drastically as an intensity of a laser is increasing. Particularly, it is shown that a charged particle exposes a spin flip resonance at a certain pick value of a laser field strength, which is determined by a particle's gyromagnetic ratio.