Photoelectron Momentum Distribution of Neon Dimer

Starting from a 2p atomic orbital aligned along the molecular axis, we solve the three-dimensional TDSE in single-active-electron approximation with the split-operator method on a Cartesian grid with 512 points in each dimension, a grid spacing of 0.25 a.u. and a time step of 0.02 a.u. While propagating up to a final time T = 1500 a.u., outgoing parts of the wave function are projected onto Volkov states^{44 (link)}. The potential for a single neon atom is chosen as in ref. ^{45 (link)} but with the singularity removed using a pseudopotential^{46 (link)} for angular momentum l = 1. The clockwise circularly polarized pulse has a 12-cycle sin² envelope and a peak field strength of 0.096 a.u. To obtain the momentum distribution for the dimer we multiply two copies of the atomic distribution by e^±ik·R/2, respectively (|R|/2 = 2.93 a.u.) and then add them coherently with an additional factor of ± 1 depending on the type of interference, gerade, or ungerade. To account for different possible orientations of the dimer with respect to the polarization plane, we vary the angle between them in 8 steps to cover a range from 0 to 45°, project the molecular photoelectron momentum distribution (PMD) onto the polarization plane and add these projections together with their geometrical weights. The PMDs are then averaged over the ATI peaks to obtain the final distributions shown in Fig. 2.