Angular Dependence of Strong Field Ionization of CH 3 X (X = F, Cl, Br, or I) Using Time-Dependent Configuration Interaction with an Absorbing Potential.

Methyl halides have been used to test basis set effects on simulations of strong field ionization using time dependent configuration interaction with an absorbing potential. Standard atom centered basis sets need to be augmented by several sets of diffuse functions on each atom so that the wave function in the strong field can interact with the absorbing potential used to model ionization. An absorbing basis of 3 s functions, 2 p functions, 3 d functions, and 1 f function is sufficient for CH3 F. Large absorbing basis sets with 4 s functions, 3 or 4 p functions, 4 or 5 d functions, and 2 f functions are recommended for the heavier halogens. The simulations used static fields in the 0.035-0.07 au range to explore the angular dependence of ionization of methyl halides. CH3 F ionizes mainly from the methyl group; CH3 Cl and CH3 Br show ionization from both the methyl group and the halogen, and CH3 I ionizes almost exclusively from the pπ orbitals of the iodine.