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.