Phys. Rev. Lett. 109, 233002 (2012)

Researchers from the USA and China have studied the characteristics of laser-induced electron diffraction that make it suitable for use as an ultrafast atomic probe. By exploiting the strong wavelength dependence of an intense laser–atom interaction, Junliang Xu and colleagues report high-resolution photoelectron momentum distributions of rare-gas atoms recorded at mid-infrared wavelengths (>100 μm). Mid-infrared lasers provide large-range momentum transfer, which is critical for achieving good spatial resolution for molecular imaging. The researchers have shown that the strong short-range atomic potential dominates the electron–ion interaction while the valence electrons remain transparent, which is a prerequisite for imaging. For recollision energies of more than 100 eV, they found that the electron–ion differential cross-sections of rare gas atoms are nearly the same for neutral atoms and singly charged ions, and that they are independent of the laser parameters.