Transitions between different channels in molecular nonsequential double ionization by few-cycle laser pulses

Abstract

The carrier-envelope-phase (CEP) dependence of correlated electron dynamics in molecular nonsequential double ionization by few-cycle laser pulses is investigated with the three-dimensional classical ensemble model. Our results show that the asymmetric longitudinal momentum spectra of the doubly charged ions strongly depend on the CEP of the laser pulses, and the CEP-dependent asymmetry in the ions' momentum spectra varies with varying internuclear distance. By tracing the classical trajectories, it is found that the ionization dynamics of the first electron greatly affects the asymmetry. Back analysis reveals that with increasing internuclear distance, the pathway responsible for energy transfer between the two electrons changes from the recollision process to the collision process. This change causes the shape of the CEP-averaged ion momentum distribution to show a double-single-triple peak structure as the internuclear distance increases.