Abstract
In strong field atomic physics community, long-range Coulomb interaction has for a long time been overlooked and its significant role in intense laser-driven photoelectron dynamics eluded experimental observations. Here we report an experimental investigation of the effect of long-range Coulomb potential on the dynamics of near-zero-momentum photoelectrons produced in photo-ionization process of noble gas atoms in intense midinfrared laser pulses. By exploring the dependence of photoelectron distributions near zero momentum on laser intensity and wavelength, we unambiguously demonstrate that the long-range tail of the Coulomb potential (i.e., up to several hundreds atomic units) plays an important role in determining the photoelectron dynamics after the pulse ends.
Highlights
In atomic physics, the Coulomb interaction no doubt plays an essential role
To shed more light on the physical origin of the ZES, we present in Fig. 5(c,d) the two dimensional photoelectron Momentum and Spatial Distributions (MSDs), i.e., the photoelectron distributions with respect to the total momentum, p, of the photoelectron and its distance from the ionic core, d, right after the laser pulse ends
Further analysis shows that these features in the momentum distributions can be attributed to the effect of the ionic Coulomb potential, especially its long range tail
Summary
The Coulomb interaction no doubt plays an essential role. Its long range characteristic is indispensable for our understanding on structure and dynamics of atoms. The VLES (energy part below ~1 eV) observed in the photoelectron spectrum is found to be connected with double-hump structure (DHS) in the momentum distributions[11,20,26] and a bunching effect has been proposed to be its underlying mechanism[20,24] In this case, the Coulomb attraction is only significant when the photoelectron moves close to the ionic core (the distance is much less than the quiver amplitude (α = E/ω2) of the electron in the laser field, which is about 100 a.u. for a typical laser field with I = 1014 W/cm[2] and λ = 2000 nm) and the energy bunching may occur even in a potential with a range of about several tens atomic units[24]. It is noteworthy that which range of the potential corresponds to the cusp structure in refs 12, 13, 16 and 17 has not been identified
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