Relativistic Photoionization Computations with the Time Dependent Dirac Equation

: Ionization of inner shell electrons by laser fields often occurs in the relativistic regime. A complete description of this phenomenon requires both relativistic and quantum mechanical treatment. The Dirac equation describes the motion of a spin one-half particle in an external electromagnetic field. The stationary states in both Coulomb and soft-core potentials are solved either analytically or numerically. These are used as initial conditions in time dependent calculations. It is found that, at least in one case, two-dimensional simulations predict a greater ionization rate than the one predicted by the Coulomb corrected strong field approximation. Computational performance is important due to the rapid oscillations in a relativistic wavefunction. Multiple General Purpose Graphical Processing Units are utilized in parallel to speed up calculations.