Ionization suppression of Cl2 molecules in intense laser fields

The strong field ionization of Cl2 molecules is investigated by using an ultrashort pulse Ti:sapphire laser. A spatial imaging technique is used in such measurements to reduce the effect of spatial integration. Cl2 shows strong ionization suppression as do other diatomic molecules having valence orbitals with antibonding symmetry (O2,S2) when compared with the field ionization of atoms with nearly identical ionization potential. A more general molecular tunneling ionization model is proposed, and the calculations are in reasonable agreement with the measurements. Our results support that antibonding leads to ionization suppression, a trend that only F2 goes against and that needs to be further investigated