Application of the weak-field asymptotic theory to the analysis of tunneling ionization of linear molecules

The recently developed weak-field asymptotic theory [Phys. Rev. A 84, 053423 (2011)] is applied to the analysis of tunneling ionization of a molecular ion (H-2(+)), several homonuclear (H-2, N-2, O-2) and heteronuclear (CO, HF) diatomic molecules, and a linear triatomic molecule (CO2) in a static electric field. The dependence of the ionization rate on the angle between the molecular axis and the field is determined by a structure factor for the highest occupied molecular orbital. This factor is calculated using a virtually exact discrete variable representation wave function for H-2(+), very accurate Hartree-Fock wave functions for the diatomics, and a Hartree-Fock quantum chemistry wave function for CO2. The structure factors are expanded in terms of standard functions and the associated structure coefficients, allowing the determination of the ionization rate for any orientation of the molecule with respect to the field, are tabulated. Our results, which are exact in the weak-field limit for H-2(+) and, in addition, under the Hartree-Fock approximation for the diatomics, are compared with results from the recent literature.