High-order harmonic generation efficiency increased by controlled dissociation of molecular iodine

We investigate the role of dissociation in high-order harmonic generation (HHG) by a vapour of molecular iodine. By controlling dissociation independently of harmonic generation we have shown for the first time that dissociation can lead to an increase in the harmonic yield. In 12, the intensity of the ninth harmonic of a 70 fs duration, 798 nm laser pulse was increased by a factor of two to three when the molecules were first dissociated by a 300 ps duration, 798 nm pulse with intensity similar to10(11) W cm(-2). These results are relevant to the interpretation of previous HHG experiments in molecules and demonstrate a straightforward technique to enhance and modulate high-order harmonic radiation.