Multielectron effects on the orientation dependence and photoelectron angular distribution of multiphoton ionization of ${\text{CO}}_2$ 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 $40°$ in good agreement with recent experimental data. Photoelectron angular distribution reveals the delicate relation between the orientation dependence and the molecular orbital symmetry.

Figure 1

(Color online) 2D sketch of molecular grids for ${\text{CO}}_2$ used in the Voronoi-cell finite difference method.

Figure 2

(Color online) Orientation dependence of total ionization probability of ${\text{CO}}_2$. ${}^{\text{a}}$Ref. 6; ${}^{\text{b}}$Ref. 7; and ${}^{\text{c}}$Ref. 26.

Figure 3

(Color online) Orientation dependence of individual ionization probability of multiple orbitals with 820 nm and $1.1\times {10}^{14}\text{W}/{\text{cm}}^2$.

Figure 4

(Color online) Photoelectron angular distribution at several orientation angles. The top panels display contour maps of $\partial P/\partial \Omega$ on the unit sphere with a vertical line of the molecular axis and an arrow line of the field polarization axis. The middle panels show the same spherical contour maps in different views that the field axis is perpendicular to the paper. The bottom panels represent polar plots of $\partial P/\partial \theta$ with a horizontal arrow line of the field axis.