Intense-field laser ionization rates in atoms and molecules

We discuss experiments on the ionization of atoms and molecules in intense laser fields, designed to facilitate a comparison of theory;and experiment especially in the case of complex molecules. We concentrate on ionization in the regime where single ionization dominates. We describe an approach which allows a direct measurement of ionization efficiencies, absolute ionization rates, and well-defined saturation intensities. In addition, intensities where multiple ionization and Coulomb explosion set in are determined. We also analyze how ion yields are sensitive to any dependence of ionization rates on molecular alignment. Application of these procedures to molecular ionization is demonstrated in detail for the organic molecules benzene and cyclohexane.