Abstract
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) x 10(14) W cm(-2), where laser-driven electron recollision leads to the population of excited states of D-2(+). Within this range we find the onset of dissociation from 3 sigma states of D-2(+) by comparing the experimental data to quantum dynamical simulations including the first eight states of D-2(+). We find that dissociation from the 3 sigma states yields D+ ions with kinetic energies above 8 eV. 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 3 sigma states: (1) excitation by electron recollision to the lower excited states, followed by laser-field excitation to the 3 sigma states, dominating at low intensities, and (2) direct excitation to the 3 sigma states by electron recollision, playing a role at higher intensities.