Carrier-Envelope Phase Dependence of Sequential Double Ionization of Nitrogen Molecules by an Intense Infrared Single-Cycle Pulse

We theoretically investigate the carrier-envelope phase (CEP) dependence of sequential double ionization (SDI) of N2 in an intense infrared single-cycle laser field using the recently developed density-matrix model. The calculated kinetic energy release (KER) spectra exhibit three peaks with clear CEP dependence. In particular, the second peak in the KER spectra is dominated by contributions from the 13Πg state of N22+, as supported by analysis of the population of this state as a function of CEP and alignment angle. At the optimal angle of 35∘, a detailed comparison of the time-dependent populations at the CEP values of 0.0π and 0.5π indicates that the CEP dependence of the populations of doubly charged states and of the signal of the second KER peak can be attributed to the CEP-dependent tunneling-ionization rates and the laser couplings between the doubly charged states. This work can shed more light on the CEP-dependent SDI of molecules driven by an intense infrared single-cycle laser pulse.