Influence of the internuclear vector on ionization of molecules in intense laser field

We theoretically study the influence of the internuclear vector on molecular ionization in linear polarization laser fields through taking O2, CO2 as model molecules. We find that the ionization rates of O2 and CO2 depend on the molecular orientations. For O2, the molecular orientation corresponding to the maximum ionization rate is about φm = 45∘, which is independent of the laser intensity; while for CO2, this kind of molecular orientation varies with laser intensity. We also find the ionization suppression of molecule depends on the molecular orientations and the internuclear distance. The ionization suppression easily disappears for molecules with larger internuclear distance.