With the fully classical ensemble model, we investigate the correlated electron dynamics of nonsequential double ionization (NSDI) by few-cycle laser pulses at 3T (T is the laser cycle) and compared it with the 6T case. For the 6T laser pulse, the momentum distribution of correlated electron in the direction parallel to the laser polarization exhibits a V-like structure which has been observed in the experiment. [Camus et al., Phys. Rev. Lett. 108, 073003 (2012)]. However, for the 3T laser pulse, the momentum distribution shows a surprising arc-like structure. Meanwhile, the correlated electron momentum spectrum in the direction perpendicular to the laser polarization shows a more stronger anticorrelated behavior for the 3T laser pulse than that of the 6T laser pulse. By analyzing all the classical trajectories of NSDI, for the 3T laser pulse, the contribution to NSDI only comes from the first return and the latter returns are completely supressed, which is different from the case of the 6T laser pulse where not only the first return but also the latter returns contribute to the NSDI events. Moreover, the recolliding energies are often higher for the 3T laser pulse than that of the 6T laser pulse due to a more rapid turn on of laser field for the 3T laser pulse which plays a key role for the arc-like structure. The more energetic recollisions that occur in the 3T laser pulse lead to greater anticorrelation in the transverse momenta than is observed in the 6T laser pulse with less energetic recollisions.
The effect of molecular alignment on correlated electron dynamics in nonsequential double ionization