Shift of the photoelectron momentum against the radiation pressure force in linearly polarized intense midinfrared laser fields

Nondipole Effects in Atomic Ionization Induced by an Intense Counter‐Rotating Bicircular Laser Field

“…There are small oscillations due to the interference of contributions originating in different cycles of the field. [ 15 ] In contrast, when the coherent sum of all SP contributions is considered, the quantity $${ \langle {p}_{z} \rangle}_{{p}_{x}}$$ exhibits rapid oscillations in the regions where two or more solutions contribute to the overall spectrum; see panel (d). In particular, for $${p}_{x}<0$$ the contributions of the solutions $$\eta =1,3$$ are significant, and their interference leads to the rapidly oscillating behavior of $${ \langle {p}_{z} \rangle}_{{p}_{x}}$$ (see Figure 1d for $${p}_{x}<0$$).…”

“…Contrary to the case of a linearly polarized field analyzed in ref. [15], these oscillations do not lead to negative values of $${ \langle {p}_{z} \rangle}_{{p}_{x}}$$ in the region where the differential ionization rate is nonnegligible. This can be explained as follows: In linearly polarized fields, the region with negative values of $${ \langle {p}_{z} \rangle}_{{p}_{x}}$$ moves away from the center of the photoelectron momentum plane with increasing wavelength.…”

“…Applying the saddle‐point (SP) approximation, the negative shift for direct photoelectrons was traced back to the interference of ionization pathways originating in the same optical cycle. [ 15 ]…”

“…Applying the saddle-point (SP) approximation, the negative shift for direct photoelectrons was traced back to the interference of ionization pathways originating in the same optical cycle. [15] Furthermore, nondipole effects for the cases of ionizing different atoms and molecules were investigated in refs. [16,17].…”