Suppression of strong-field ionization by optimal pulse shaping: Application to hydrogen and the hydrogen molecular ion

We investigate the ability of quantum optimal control theory to shape pulses suppressing strong-field ionization of a hydrogen atom and a H-2(+) molecule. We show that considerable suppression of the ionization yield can be achieved for both H and H-2(+) with optimal pulse shaping for a fixed fluence and pulse length. The mechanisms responsible for ionization suppression and the shape of the optimized pulse are different for infrared and ultraviolet laser fields. In the low-frequency regime the optimized pulse reduces the ionization yield by suppressing the highest peaks of the laser field. For the higher laser frequencies considered the ionization yield of H can be decreased by exciting low-lying resonances.