Intensity dependence of the attosecond control of the dissociative ionization of D₂

Light-field driven electron localization in deuterium molecules in intense near single-cycle laser fields is studied as a function of the laser intensity. The emission of D⁺ions from the dissociative ionization of D ₂ is interrogated with single-shot carrier-envelope phase (CEP)-tagged velocity map imaging. We explore the reaction for an intensity range of (1.0-2.8)10¹⁴W cm^-2, where laser-driven electron recollision leads to the population of excited states of D2⁺. Within this range we find the onset of dissociation from 3σ states of D 2 ⁺by comparing the experimental data to quantum dynamical simulations including the first eight states of D2⁺. We find that dissociation from the 3σ states yields D⁺ions with kinetic energies above 8eV. Electron localization in the dissociating molecule is identified through an asymmetry in the emission of D⁺ions with respect to the laser polarization axis. The observed CEP-dependent asymmetry indicates two mechanisms for the population of 3σ states: (1) excitation by electron recollision to the lower excited states, followed by laser-field excitation to the 3σ states, dominating at low intensities, and (2) direct excitation to the 3σ states by electron recollision, playing a role at higher intensities.