Strong-field control of electron localisation during molecular dissociation

We demonstrate how the waveform of light can be used to control a molecular dissociation by the steering and localisation of electrons. Experimental results have been obtained for the dissociative ionisation of the homonuclear and heteronuclear hydrogen derivates D(2) and HD. Asymmetric ejection of the ionic fragments reveals that light-driven electronic motion prior to dissociation localises the electron on one of the two ions in diatomic molecular ions in a controlled way. Extension of these results to electron transfer in complex molecules suggests a new paradigm for controlling photochemistry.