Multielectron effects on the orientation dependence and photoelectron angular distribution of multiphoton ionization of CO2 in strong laser fields

We perform an ab initio study of multiphoton ionization (MPI) of carbon dioxide in intense linearly polarized laser pulses with arbitrary molecular orientation by means of a time-dependent density-functional theory (TDDFT) with proper long-range potential. We develop a time-dependent Voronoi-cell finite difference method with highly adaptive molecular grids for accurate solution of the TDDFT equations. Our results demonstrate that the orientation dependence of MPI is determined by multiple orbital contributions and that the electron correlation effects are significant. The maximum peak of MPI is predicted to be at 40 deg. in good agreement with recent experimental data. Photoelectron angular distribution reveals the delicate relation between the orientation dependence and the molecular orbital symmetry.