Intensity dependence of the dissociative ionization of DCl in few-cycle laser fields

We have studied the dissociative ionization of DCl in 4 fs laser fields at 720 nm central wavelength using intensities in the range (1.3-3.1) × 10¹⁴ W cm^-2. By employing the phase-tagged velocity-map imaging technique, information about the angular distribution of deuterium ions as a function of their kinetic energy and the carrier-envelope phase is obtained. On the basis of the experimental data and semi-classical simulations, three regions are distinguished for the resulting D⁺ ions with different kinetic energies. The one with the lowest kinetic energy, around 5-7 eV, is from dissociation involving the X-state of DCl⁺, populated through direct ionization with the laser field. The second region, around 7-11 eV, originates from rescattering induced dissociative ionization. Above 2 × 10¹⁴ W cm^-2 D⁺ ions with kinetic energies exceeding 15 eV are obtained, which we ascribe to double ionization induced by rescattered electrons.