Attosecond interference induced by Coulomb-field-driven transverse backward-scattering electron wave packets

A universal interference structure is found in the photoelectron momentum distribution of atoms in intense infrared laser field. Theoretical analysis shows that this structure can be attributed to a form of Coulomb-field-driven backward-scattering photoelectrons in the direction perpendicular to the laser field, in contrast to the conventional rescattering along the laser polarization direction. This transverse backward-scattering process is closely related to a family of photoelectrons initially ionized within a time interval of less than 200 as around the crest of the laser electric field. Those electrons, acquiring near-zero return energy in the laser field, will be pulled back solely by the ionic Coulomb field and backscattered in the transverse direction. Moreover, this rescattering process mainly occurs at the first or second return time, giving rise to different phases of the photoelectrons. The interference between these photoelectrons leads to unique curved interference fringes which are observable for most current intense field experiments, opening another way to record the electron dynamics in atoms and molecules on a time scale much shorter than an optical cycle.National Key Program for S&T Research and Development [2016YFA0401100]; National Basic Research Program of China [2013CB922201]; NNSF of China [11374202, 11674209, 11274220, 11334009, 11425414]; Major Program of Guangdong Natural Science Foundation [2014A030311019]; Open Fund of the State Key Laboratory of High Field Laser Physics (SIOM); "YangFan" Talent Project of Guangdong ProvinceSCI(E)ARTICLE39