Investigation of Angular Dependence of Strong-Field Tunneling Ionization for Asymmetric Diatomic Molecule HeH2+

We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH2+ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schrödinger equation with B-spline basis. Then the angular dependence of strong-field ionization rates of HeH2+ are investigated with the molecular tunneling ionization theory. We show that the shape of several lowly excited states (i.e. 2pσ, 2pπ, 3dδ) for HeH2+ are reflected in the orientation dependent ionization rates very well, however, the angle-dependent ionization rate fails to follow the angular distribution of the asymptotic electron density for the ground state 1sσ. We also show that the internuclear distance dependent ionization probabilities are in a good agreement with the more accurate result obtained from the numerical solution of the time-dependent Schrödinger equation.